EXHIBIT 10.29.4





                          REGISTRATION RIGHTS AGREEMENT



                          dated as of September 7, 2001

                                  by and among

                                  PROBEX CORP.

                                     and the

                               Investors listed on

                                Schedule A hereto












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                                                     TABLE OF CONTENTS




     1.  DEFINITIONS.......................................................1

     2.  REGISTRATION......................................................2

     3.  OBLIGATIONS OF THE COMPANY........................................3

     4.  OBLIGATIONS OF THE INVESTORS......................................7

     5.  EXPENSES OF REGISTRATION..........................................8

     6.  INDEMNIFICATION...................................................8

     7.  CONTRIBUTION.....................................................10

     8.  REPORTS UNDER THE EXCHANGE ACT...................................10

     9.  INFORMATION RIGHTS...............................................11

    10.  INSPECTION RIGHTS................................................11

    11.  ASSIGNMENT OF REGISTRATION RIGHTS................................11

    12.  AMENDMENT OF REGISTRATION RIGHTS.................................12

    13.  TERMINATION OF REGISTRATION RIGHTS...............................12

    14.  GENERAL PROVISIONS...............................................12

    SCHEDULE A...........................................................S-A

    SCHEDULE B...........................................................S-B

    EXHIBIT A............................................................E-A



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                          REGISTRATION RIGHTS AGREEMENT

         THIS REGISTRATION  RIGHTS AGREEMENT (this  "Agreement"),  is made as of
September 7, 2001, by and among Probex Corp., a Delaware  corporation,  with its
headquarters  located at 13355 Noel Road, Suite 1200,  Dallas,  Texas 75240 (the
"Company"),  and the Investors  listed on Schedule A attached  hereto  (together
with  their  respective  affiliates  and any  assignee  or  transferee  of their
respective rights hereunder, the "Investors").

         WHEREAS,  in connection with those certain Secured  Promissory Notes in
the aggregate principal amount of $3,000,000 made by the Company in favor of the
Investors,  or their nominees, of even date herewith (the "Notes"),  the Company
has agreed,  upon the terms and subject to the conditions  contained therein, to
issue to the Investors  certain shares of its common and/or preferred stock (the
"Stock").

         WHEREAS, to induce the Investors to purchase the Notes, the Company has
agreed to provide (a) certain  registration  rights under the  Securities Act of
1933,  as  amended,  and the rules and  regulations  thereunder,  or any similar
successor  statute  (collectively,  the "Securities  Act"), and applicable state
securities laws; and (b) certain other rights as set forth herein.

         NOW,  THEREFORE,  in  consideration  of the  premises  and  the  mutual
covenants  contained  herein  and other  good and  valuable  consideration,  the
receipt and  sufficiency of which are hereby  acknowledged,  the Company and the
Investors hereby agree as follows:

         1. DEFINITIONS.

         (a) As used in this  Agreement,  the  following  terms  shall  have the
following meanings:

                  (i) "Common  Stock" means the Company's  common stock,  $0.001
par value per share.

                  (ii)  "Investors"  means the Investors  and any  transferee or
assignee  who agrees to become  bound by the  provisions  of this  Agreement  in
accordance with Section 11 hereof and who executes a form of Joinder  Agreement,
attached hereto as Exhibit A.

                  (iii) "register,"  "registered," and "registration" refer to a
registration  effected  by  preparing  and filing a  Registration  Statement  or
Statements in compliance  with the Securities Act and pursuant to Rule 415 under
the Securities Act or any successor rule providing for offering  securities on a
continuous  basis ("Rule 415"), and the declaration or ordering of effectiveness
of such  Registration  Statement by the United States of America  Securities and
Exchange Commission (the "SEC").

                  (iv) "Registrable Securities" means the shares of Common Stock
issued to the  Investors  pursuant  to  Section 4 of the Notes and the shares of
Common Stock issued to Investors,  or issuable upon the Investors' conversion of
the preferred stock issued to Investors, pursuant to the Section 3 of the Notes.

                  (v)  "Registration  Statement" means one or more  registration
statements of the Company filed with the SEC under the  Securities  Act pursuant
to this Agreement.


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         (b)  Capitalized  terms used herein and not  otherwise  defined  herein
shall have the respective meanings set forth in the Notes.

         2. REGISTRATION.

         (a) Mandatory  Registration.  The Company shall prepare and file within
thirty (30) days after the closing date of the Qualified Equity Financing or the
Final  Maturity Date, if earlier,  a Registration  Statement on Form S-1 or Form
SB-2 (or, if available,  on Form S-3, or if Form S-3 is not  available,  on such
form of Registration  Statement as is then available to effect a registration of
the Registrable Securities) with the SEC, covering the resale of the Registrable
Securities  to  enable  the  resale  by the  Investors  from time to time on the
American Stock Exchange (the "AMEX") or in privately-negotiated  transactions or
otherwise.  The Company shall register all of the Registrable  Securities on the
Registration Statement;  provided,  however, that if the Company determines that
not all of the  Registrable  Securities  can be registered  on one  Registration
Statement,  then the  Company  will  file a  Registration  Statement  as soon as
practicable following the issuance of any Registrable  Securities not registered
prior  to  issuance.   The  Company   shall  use  its  best  efforts  to  obtain
effectiveness   of  the   Registration   Statement   as  soon  as   practicable.
Notwithstanding  the  foregoing,  if the Company  shall  furnish the Investors a
certificate  signed by the  President  of the Company  stating  that in the good
faith  judgment of the Board of Directors of the Company,  it would be seriously
detrimental to the Company and its stockholders for such Registration  Statement
to be  filed  and  it is  therefore  essential  to  defer  the  filing  of  such
Registration  Statement,  the Company  shall have the right to defer such filing
for a period of not more than  ninety  (90) days from the Final  Maturity  Date;
provided, however, that the Company may not utilize this right more than once.

         (b)  Piggy-Back  Registrations.  Subject to the last  sentence  of this
Section 2(b), if at any time prior to the expiration of the Registration  Period
(as  defined in  Section  3(a)  hereof)  the  Company  shall file with the SEC a
Registration  Statement  relating  to an  offering  for its own  account  or the
account  of others  under the  Securities  Act of any of its  equity  securities
(other than on Form S-4 or Form S-8 or their then equivalents relating to equity
securities to be issued solely in connection  with any acquisition of any entity
or business or equity  securities  issuable in  connection  with stock option or
other employee benefit plans),  the Company shall send to the Investors  written
notice  of such  determination  and,  if  within  fifteen  (15)  days  after the
effective date of such notice,  the Investors  shall so request in writing,  the
Company  shall  include in such  Registration  Statement  all or any part of the
Registrable  Securities the Investors request to be registered,  except that if,
in  connection  with any  underwritten  public  offering  for the account of the
Company the managing  underwriter(s)  thereof  shall impose a limitation  on the
number of  shares of Common  Stock  which may be  included  in the  Registration
Statement because,  in such underwriter's  judgment,  marketing or other factors
dictate such limitation is necessary to facilitate public distribution, then the
Company shall be obligated to include in such  Registration  Statement only such
limited portion of the Registrable Securities with respect to which the Investor
has requested  inclusion  hereunder as the underwriter  shall permit;  provided,
however,  that the Company shall not exclude any Registrable  Securities  unless
the Company has first excluded all outstanding securities,  the holders of which
are not entitled to inclusion of such securities in such Registration  Statement
or are not entitled to pro rata inclusion with the Registrable  Securities;  and
provided,  further,  however,  that,  after  giving  effect  to the  immediately
preceding  proviso,  any exclusion of Registrable  Securities  shall be made pro
rata  with  holders  of  other  securities  having  the  right to  include  such
securities  in the  Registration  Statement  other than  holders  of  securities
entitled to  inclusion of their  securities  in such  Registration  Statement by
reason of priority  registration rights. No right to registration of Registrable
Securities  under this Section 2(b) shall be construed to limit any registration


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required  under  Section 2(a) hereof.  If an offering in which the Investors are
entitled to registration  under this Section 2(b) is an  underwritten  offering,
then  the  Investors   whose   Registrable   Securities  are  included  in  such
Registration  Statement shall, unless otherwise agreed by the Company, offer and
sell such  Registrable  Securities in an  underwritten  offering  using the same
underwriter or underwriters and, subject to the provisions of this Agreement, on
the same terms and  conditions as other shares of Common Stock  included in such
underwritten  offering. The Company shall not be obligated to effect, or to take
any action to effect, any registration  pursuant to this Section 2(b), after the
Company has  effected  at least one (1)  registration  pursuant to this  Section
2(b), which includes all Registrable  Securities and such  registration has been
declared effective by the SEC.

         (c)  Notwithstanding  anything to the  contrary set forth  herein,  the
registration  rights of the Investors  pursuant to Section 2(b) above shall only
be available in the event the Company fails to timely file, obtain effectiveness
or maintain  effectiveness of the Registration Statement to be filed pursuant to
Section  2(a) in  accordance  with the  terms of this  Agreement;  however,  the
availability of such registration  rights under Section 2(b) shall not be deemed
to cure any breach of the Company's  obligations  under Section 2(a),  nor shall
the use of any of such  rights  by any  Investor  be deemed a waiver of any such
rights or any right to damages resulting therefrom.

         3. OBLIGATIONS OF THE COMPANY.

         In connection with the registration of the Registrable Securities,  the
Company shall have the following obligations:

         (a)  The  Company  shall  prepare  promptly  and  file  a  Registration
Statement  with the SEC in accordance  with Section 2(a) hereof,  and thereafter
use its best efforts to cause such Registration Statement to become effective as
soon as  possible  after  such  filing,  and  keep  the  Registration  Statement
effective pursuant to Rule 415 at all times until such date as is the earlier of
(i) the date on which all of the Registrable  Securities have been sold, or (ii)
the date on which the  Registrable  Securities (in the opinion of counsel to the
Investor)  may  be  immediately  sold  without  restriction  (including  without
limitation as to volume by each holder thereof) without  registration  under the
Securities  Act  (the  "Registration  Period"),   which  Registration  Statement
(including  any  amendments or supplements  thereto and  prospectuses  contained
therein)  shall not contain any untrue  statement of a material  fact or omit to
state a material  fact required to be stated  therein,  or necessary to make the
statements therein not misleading.

         (b) The Company  shall  prepare  and file with the SEC such  amendments
(including  post-effective  amendments)  and  supplements  to  the  Registration
Statement and the prospectus used in connection with the Registration  Statement
as may be necessary to keep the  Registration  Statement  effective at all times
during the  Registration  Period,  and,  during  such  period,  comply  with the
provisions  of  the  Securities  Act  with  respect  to the  disposition  of all
Registrable  Securities  of the Company  covered by the  Registration  Statement
until such time as all of such  Registrable  Securities have been disposed of in
accordance  with the intended  methods of  disposition  by the seller or sellers
thereof as set forth in the Registration Statement.

         (c) The  Company  shall  furnish  to the  Investors  whose  Registrable
Securities are included in the  Registration  Statement and to its legal counsel
(i) promptly after the same is prepared and publicly distributed, filed with the
SEC, or received by the Company, one copy of the Registration  Statement and any
amendment thereto, each preliminary prospectus and prospectus and each amendment
or supplement thereto,  and, in the case of the Registration  Statement referred


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to in Section  2(a),  each letter  written by or on behalf of the Company to the
SEC or the staff of the SEC, and each item of correspondence from the SEC or the
staff of the SEC, in each case relating to such  Registration  Statement  (other
than any portion  thereof which contains  information  for which the Company has
sought confidential treatment),  and (ii) such number of copies of a prospectus,
including preliminary  prospectuses,  and all amendments and supplements thereto
and such other  documents as the  Investors may  reasonably  request in order to
facilitate the disposition of the Registrable Securities owned by the Investors.
The Company will promptly notify the Investors by facsimile of the effectiveness
of the Registration Statement or any post-effective  amendment. The Company will
promptly  respond to any and all  comments  received  from the SEC,  with a view
towards  causing  any  Registration  Statement  or any  amendment  thereto to be
declared  effective by the SEC as soon as practicable and shall promptly file an
acceleration  request  as  soon  as  practicable  following  the  resolution  or
clearance of all SEC comments or, if applicable,  following  notification by the
SEC that the Registration Statement or any amendment thereto will not be subject
to review.

         (d) The Company  shall use its best efforts to (i) register and qualify
the  Registrable  Securities  covered by the  Registration  Statement under such
other  securities or "blue sky" laws of such  jurisdictions in the United States
as the Investors,  holding Registrable  Securities being offered, may reasonably
request, (ii) prepare and file in those jurisdictions such amendments (including
post-effective   amendments)   and   supplements  to  such   registrations   and
qualifications as may be necessary to maintain the effectiveness  thereof during
the  Registration  Period,  (iii) take such other actions as may be necessary to
maintain such registrations and qualifications in effect at all times during the
Registration  Period,  and (iv) take all other actions  reasonably  necessary or
advisable to qualify the Registrable  Securities for sale in such jurisdictions;
provided,  however,  that  the  Company  shall  not be  required  in  connection
therewith  or as a  condition  thereto  to (a)  qualify  to do  business  in any
jurisdiction  where it would not  otherwise  be required to qualify but for this
Section 3(d), (b) subject itself to general  taxation in any such  jurisdiction,
(c) file a general consent to service of process in any such  jurisdiction,  (d)
provide any undertakings  that cause the Company undue expense or burden, or (e)
make any  change  in its  charter  or  bylaws,  which in each  case the Board of
Directors of the Company  determines to be contrary to the best interests of the
Company and its stockholders.

         (e) As promptly as practicable  after becoming aware of such event, the
Company  shall notify the  Investors of the  happening of any event of which the
Company  has  knowledge,  as a result of which the  prospectus  included  in the
Registration  Statement,  as then in effect,  includes an untrue  statement of a
material fact or omission to state a material fact required to be stated therein
or necessary to make the  statements  therein not  misleading,  and use its best
efforts  promptly  to prepare a  supplement  or  amendment  to the  Registration
Statement to correct such untrue statement or omission,  and deliver such number
of  copies  of such  supplement  or  amendment  to the  Investors  as  they  may
reasonably request.

         (f) The Company  shall use its best  efforts to prevent the issuance of
any stop order or other suspension of effectiveness of a Registration  Statement
and, if such an order is issued,  to obtain the  withdrawal of such order at the
earliest  possible  moment and to notify the  Investors,  holders of Registrable
Securities  being  sold  (or,  in the  event of an  underwritten  offering,  the
managing  underwriters),  of the  issuance  of such  order  and  the  resolution
thereof.

         (g) The Company shall permit  counsel to the  Investors,  as holders of
the  Registrable  Securities,  to  review  the  Registration  Statement  and all
amendments and supplements  thereto (as well as all requests for acceleration or
effectiveness  thereof) a  reasonable  period of time prior to their filing with
the SEC,  and the  Company  will not file any  document  in a form to which such


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counsel reasonably objects and the Company will not request  acceleration of the
Registration  Statement without prior notice to such counsel.  In the event of a
disagreement between the Investors and the Company regarding any action taken by
the Company to which  counsel to the  Investors  objects  (the  "Dispute"),  the
Investors shall give written notice (the "Dispute Notice") of the Dispute to the
Company,  delivered in  accordance  with Section  14(b) of this  Agreement.  The
Dispute  Notice  shall  set  forth  in  reasonable  detail  the  Dispute  of the
Investors.  Upon receipt of the Dispute Notice,  the date upon which the Company
is required to file the Registration  Statement  pursuant to Section 2(a) hereof
shall be extended by the number of elapsed  day(s) of the Dispute.  The sections
of  the  Registration   Statement  covering  information  with  respect  to  the
Investors,  Investors' beneficial ownership of securities of the Company, or the
Investors'  intended  method of  disposition  of  Registrable  Securities  shall
conform to the information provided to the Company by the Investors.

         (h) At the request of the Investors,  the Company shall furnish, on the
date that  Registrable  Securities are delivered to an underwriter,  if any, for
sale in connection  with the  Registration  Statement or, if such securities are
not being sold by an underwriter,  on the date of  effectiveness  thereof (i) an
opinion,  dated as of such date,  from  counsel  representing  the  Company  for
purposes of such  Registration  Statement,  in form,  scope and  substance as is
customarily  given  in  an  underwritten  public  offering,   addressed  to  the
underwriters,  if any, and the  Investors,  and (ii) a letter,  dated such date,
from  the  Company's  independent  certified  public  accountants,  in form  and
substance as is customarily given by independent certified public accountants to
underwriters in an underwritten public offering,  addressed to the underwriters,
if any, and the Investors.

         (i) In the event of any underwritten public offering, the Company shall
enter into and perform its obligations under an underwriting agreement, in usual
and  customary  form,  with  the  managing  underwriter  of such  offering.  The
Investors  participating  in such an  underwriting  shall  also  enter  into and
perform their obligations under such an agreement.

         (j)  The  Company  shall  make  available  for  inspection  by (i)  the
Investors, (ii) any underwriter participating in any disposition pursuant to the
Registration Statement,  (iii) one firm of attorneys and one firm of accountants
or  other  agents   retained  by  the  Investors   and  all  such   underwriters
(collectively,  the "Inspectors") all pertinent financial and other records, and
pertinent corporate documents and properties of the Company  (collectively,  the
"Records"),  as shall be reasonably deemed necessary by each Inspector to enable
each  Inspector  to exercise  its due  diligence  responsibility,  and cause the
Company's officers,  directors and employees to supply all information which any
Inspector may reasonably  request for purposes of such due diligence;  provided,
however,  that each  Inspector  shall hold in confidence  and shall not make any
disclosure  (except to the  Investors  or  underwriters)  of any Record or other
information which the Company  determines in good faith to be confidential,  and
of which determination the Inspectors are so notified, unless (a) the disclosure
of such Records is necessary to avoid or correct a  misstatement  or omission in
any Registration Statement,  (b) the release of such Records is ordered pursuant
to a  subpoena  or other  order  from a court or  government  body of  competent
jurisdiction,  or (c) the  information  in such Records has been made  generally
available  to the public  other than by  disclosure  in violation of this or any
other agreement.  The Company shall not be required to disclose any confidential
information  in such Records to any  Inspector  until and unless such  Inspector
shall  have  entered  into  confidentiality  agreement  (in form  and  substance
satisfactory   to  the  Company)   with  the  Company   with  respect   thereto,
substantially  in the form of this Section 3(j).  The Investors  agree that they
shall,  upon learning that disclosure of such Records is sought in or by a court
or  governmental  body of competent  jurisdiction  or through other means,  give


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prompt notice to the Company and allow the Company, at its expense, to undertake
appropriate  action to prevent  disclosure  of, or to obtain a protective  order
for,  the  Records  deemed  confidential.   Nothing  herein  (or  in  any  other
confidentiality agreement between the Company and the Investors) shall be deemed
to limit the Investors' ability to sell Registrable Securities in a manner which
is otherwise consistent with applicable laws and regulations.

         (k) The Company shall hold in confidence and not make any disclosure of
information  concerning  the  Investors  provided  to  the  Company  unless  (i)
disclosure  of such  information  is  necessary  to comply with federal or state
securities  laws, (ii) the disclosure of such  information is necessary to avoid
or correct a misstatement or omission in any Registration  Statement,  (iii) the
release of such  information  is ordered  pursuant  to a subpoena or other order
from a court  or  governmental  body of  competent  jurisdiction,  or (iv)  such
information  has been made  generally  available  to the  public  other  than by
disclosure in violation of this or any other agreement.  The Company agrees that
it shall,  upon learning  that  disclosure of such  information  concerning  the
Investors is required under clause (i) or clause (ii) above,  or is sought in or
by a court or  governmental  body of  competent  jurisdiction  or through  other
means,  give  prompt  notice to the  applicable  Investor  prior to making  such
disclosure,  and allow the  applicable  Investor,  at its expense,  to undertake
appropriate  action to prevent  disclosure  of, or to obtain a protective  order
for, such information.

         (l) The Company shall (i) cause all the Registrable  Securities covered
by the Registration  Statement to be listed on each national securities exchange
on which  securities  of the same class or series issued by the Company are then
listed, including,  without limitation, the AMEX, if any, if the listing of such
Registrable  Securities is then permitted  under the rules of such exchange,  or
(ii) secure the  designation and quotation,  of all the  Registrable  Securities
covered by the Registration  Statement on the Nasdaq or, if not eligible for the
Nasdaq on the Nasdaq  SmallCap  and,  without  limiting  the  generality  of the
foregoing,  to arrange for at least two (2) market  makers to register  with the
National  Association  of  Securities  Dealers,  Inc.  (the "NASD") as such with
respect to such Registrable Securities.

         (m) The Company shall provide a transfer agent and registrar, which may
be a single entity, for the Registrable  Securities not later than the effective
date of the Registration Statement.

         (n) The  Company  shall  cooperate  with the  Investors,  as holders of
Registrable   Securities  being  offered,   and  the  managing   underwriter  or
underwriters,  if any, to  facilitate  the timely  preparation  and  delivery of
certificates  (not bearing any  restrictive  legends)  representing  Registrable
Securities to be offered pursuant to the Registration  Statement and enable such
certificates to be in such denominations or amounts,  as the case may be, as the
managing  underwriter or  underwriters,  if any, or the Investors may reasonably
request  and   registered  in  such  names  as  the  managing   underwriter   or
underwriters,  if any, or the  Investors  may  request,  and,  within  three (3)
business  days  after  a  Registration   Statement  which  includes  Registrable
Securities is ordered effective by the SEC, the Company shall deliver, and shall
cause legal counsel  selected by the Company to deliver,  to the transfer  agent
for the Registrable Securities (with copies to the Investors,  whose Registrable
Securities  are  included in such  Registration  Statement)  an  instruction  in
customary form and substance and an opinion of such counsel,  if required by the
transfer agent, in customary form and substance.

         (o)  At the  request  of  the  Investors,  as  holders  of  Registrable
Securities,  the Company shall  prepare and file with the SEC,  such  amendments
(including   post-effective   amendments)  and  supplements  to  a  Registration


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Statement and the prospectus used in connection with the Registration  Statement
as may be  necessary  in order to change the plan of  distribution  set forth in
such Registration Statement.

         (p) In the event that the Investors  transfer or assign any Registrable
Securities in accordance with Section 11 hereof,  the Company will supplement or
amend the  Registration  Statement  to allow for the  transferee  or assignee to
effect sales of Registrable Securities pursuant to the Registration Statement.

         (q) The Company shall take all other  reasonable  actions  necessary to
expedite and facilitate  disposition by the Investors of Registrable  Securities
pursuant to the Registration Statement.

         (r) The Company shall cause all  Registrable  Securities to be approved
for listing on the American Stock Exchange prior to the earlier of (i) the Final
Extension Date (as defined in the Notes) or (ii) the filing of the  Registration
Statement with the SEC.

         4. OBLIGATIONS OF THE INVESTOR.

         In connection with the registration of the Registrable Securities,  the
Investors shall have the following obligations:

         (a) It shall be a condition precedent to the obligations of the Company
to any Investor to complete the  registration  pursuant to this  Agreement  that
such Investor shall furnish to the Company such  information  regarding  itself,
the  Registrable  Securities  held by such  Investor and the intended  method of
disposition  of the  Registrable  Securities  held by such  Investor as shall be
reasonably  required to effect the registration of such  Registrable  Securities
and shall execute such  documents in connection  with such  registration  as the
Company may  reasonably  request.  At least three (3) business days prior to the
first anticipated filing date of the Registration  Statement,  the Company shall
notify the Investors of the information the Company requires from each Investor.

         (b) By the Investors'  acceptance of the  Registrable  Securities,  the
Investors  agree to cooperate  with the Company as  reasonably  requested by the
Company  in  connection  with the  preparation  and  filing of the  Registration
Statement  hereunder,  unless an Investor has notified the Company in writing of
its election to exclude all of its Registrable  Securities from the Registration
Statement.

         (c) The  Investors  agree  that,  upon  receipt of any notice  from the
Company of the  happening of any event of the kind  described in Section 3(e) or
Section 3(f) hereof, the Investors will immediately  discontinue  disposition of
Registrable  Securities  pursuant to the  Registration  Statement  covering such
Registrable  Securities  until  the  Investors'  receipt  of the  copies  of the
supplemented or amended prospectus  contemplated by Section 3(e) or Section 3(f)
hereof and, if so directed by the Company,  the  Investors  shall deliver to the
Company (at the expense of the Company) or destroy (and deliver to the Company a
certificate  of  destruction)  all copies in the  Investors'  possession  of the
prospectus  covering such Registrable  Securities current at the time of receipt
of such notice.

         (d) An Investor may not  participate in any  underwritten  registration
hereunder  unless the Investor (i) agrees to sell its Registrable  Securities on
the basis provided in any underwriting  arrangements in usual and customary form
entered into by the Company,  (ii)  completes  and executes all  questionnaires,
powers of attorney,  indemnities,  underwriting  agreements and other  documents


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reasonably required under the terms of such underwriting arrangements, and (iii)
agrees to pay its pro rata share of all underwriting discounts and commissions.

         5. EXPENSES OF REGISTRATION.

         All  expenses,  other  than  underwriting  discounts  and  commissions,
incurred in connection with registrations, filings or qualifications pursuant to
Sections 2 and 3 hereof, including without limitation all registration,  listing
and qualification fees, printers and accounting fees, the fees and disbursements
of counsel for the Company,  and the reasonable  fees and  disbursements  of one
counsel selected by the Investors, shall be borne by the Company.

         6. INDEMNIFICATION.

         In the event any Registrable  Securities are included in a Registration
Statement under this Agreement:

         (a) To the extent  permitted by law, the Company will  indemnify,  hold
harmless and defend (i) the Investors, as holders of Registrable Securities, and
Zesiger  Capital  Group,  LLC ("ZCG"),  (ii) the directors,  officers,  members,
managers,  partners,  trustees,  employees  and  agents of and each  person  who
controls the Investor within the meaning of the Securities Act or the Securities
Exchange Act of 1934, as amended (the "Exchange  Act"), if any, or ZCG (iii) any
underwriter (as defined in the Securities  Act), if any, and (iv) the directors,
officers,  partners, employees and each person who controls any such underwriter
within the meaning of the Securities  Act or the Exchange Act, if any (each,  an
"Indemnified  Person"),  against any joint or several losses,  claims,  damages,
liabilities  or expenses  (collectively,  together with actions,  proceedings or
inquiries by any regulatory or self-regulatory  organization,  whether commenced
or  threatened,  in respect  thereof,  "Claims") to which any of them may become
subject  insofar as such Claims  arise out of or are based upon:  (i) any untrue
statement  or alleged  untrue  statement  of a material  fact in a  Registration
Statement or the omission or alleged  omission to state  therein a material fact
required  to  be  stated  or  necessary  to  make  the  statements  therein  not
misleading;  (ii) any untrue statement or alleged untrue statement of a material
fact contained in any preliminary prospectus if used prior to the effective date
of such Registration Statement, or contained in the final prospectus (as amended
or  supplemented,  if the  Company  files any  amendment  thereof or  supplement
thereto with the SEC) or the omission or alleged  omission to state  therein any
material fact  necessary to make the  statements  made therein,  in light of the
circumstances  under which the statements therein were made, not misleading;  or
(iii) any violation or alleged  violation by the Company of the Securities  Act,
the  Exchange  Act,  any other law,  including,  without  limitation,  any state
securities  law, or any rule or regulation  thereunder  relating to the offer or
sale of the  Registrable  Securities  (the matters in the foregoing  clauses (i)
through (iii) being,  collectively,  "Violations").  Subject to the restrictions
set forth in Section  6(c) hereof with  respect to the number of legal  counsel,
the Company shall  reimburse the Indemnified  Person,  promptly as such expenses
are  incurred and are due and payable,  for any  reasonable  legal fees or other
reasonable  expenses  incurred  by  them in  connection  with  investigating  or
defending  any such Claim.  Notwithstanding  anything to the contrary  contained
herein, the indemnification  agreement contained in this Section 6(a): (i) shall
not apply to a Claim  arising out of or based upon a Violation  which  occurs in
reliance upon and in  conformity  with  information  furnished in writing to the
Company by any  Indemnified  Person or underwriter for such  Indemnified  Person
expressly  for  use in  connection  with  the  preparation  of the  Registration
Statement  or  any  such  amendment  thereof  or  supplement  thereto,  if  such
prospectus  was timely made  available  by the Company  pursuant to Section 3(c)


                                       8
<PAGE>

hereof;  (ii) shall not apply to amounts paid in settlement of any Claim if such
settlement is effected  without the prior written consent of the Company,  which
consent  shall not be  unreasonably  withheld;  and (iii)  with  respect  to any
preliminary prospectus, shall not inure to the benefit of any Indemnified Person
if  the  untrue  statement  or  omission  of  material  fact  contained  in  the
preliminary  prospectus  was corrected on a timely basis in the  prospectus,  as
then  amended  or  supplemented,  such  corrected  prospectus  was  timely  made
available by the Company  pursuant to Section 3(c) hereof,  and the  Indemnified
Person was promptly advised in writing not to use the incorrect prospectus prior
to  the  use  giving  rise  to  a  Violation   and  such   Indemnified   Person,
notwithstanding  such advice, used it. Such indemnity shall remain in full force
and  effect  regardless  of  any  investigation  made  by or on  behalf  of  the
Indemnified Person and shall survive the transfer of the Registrable  Securities
by the Investor, pursuant to Section 11.

         (b)  In  connection  with  any  Registration  Statement  in  which  the
Investors are  participating,  the Investors  agree severally and not jointly to
indemnify,  hold harmless and defend,  to the same extent and in the same manner
set forth in Section 6(a) hereof,  the Company,  each of its directors,  each of
its  officers who signs the  Registration  Statement,  each person,  if any, who
controls the Company  within the meaning of the  Securities  Act or the Exchange
Act,  any  underwriter,  and any other  Investor  or other  stockholder  selling
securities  pursuant to the Registration  Statement and each of their respective
directors, officers, trustees, members, managers and employees or any person who
controls such Investor,  stockholder  or  underwriter  within the meaning of the
Securities  Act  or  the  Exchange  Act   (collectively  and  together  with  an
Indemnified Person, an "Indemnified  Party"),  against any Claim to which any of
them  may  become  subject,  under  the  Securities  Act,  the  Exchange  Act or
otherwise, insofar as such Claim arises out of or is based upon any Violation by
an  Investor,  in each case to the  extent  (and only to the  extent)  that such
Violation  occurs in reliance  upon and in conformity  with written  information
about the Investor furnished to the Company by the Investor expressly for use in
connection with such Registration Statement; and subject to Section 6(c) hereof,
the  Investor  will  reimburse  any legal or other  expenses  (promptly  as such
expenses are incurred  and are due and payable)  reasonably  incurred by them in
connection with  investigating or defending any such Claim;  provided,  however,
that the indemnity  agreement  contained in this Section 6(b) shall not apply to
amounts paid in settlement of any Claim if such  settlement is effected  without
the  prior  written  consent  of  the  Investor,  which  consent  shall  not  be
unreasonably withheld;  provided,  further,  however, that the Investor shall be
liable under this Agreement  (including  this Section 6(b) and Section 7 hereof)
for only that amount as does not exceed the net  proceeds  to the  Investor as a
result  of the sale of  Registrable  Securities  pursuant  to such  Registration
Statement.  Such indemnity  shall remain in full force and effect  regardless of
any  investigation  made by or on  behalf  of such  Indemnified  Party and shall
survive the transfer of the Registrable Securities by the Investor,  pursuant to
Section 11 hereof.  Notwithstanding  anything to the contrary  contained herein,
the indemnification agreement contained in this Section 6(b) with respect to any
preliminary  prospectus shall not inure to the benefit of any Indemnified  Party
if  the  untrue  statement  or  omission  of  material  fact  contained  in  the
preliminary  prospectus  was corrected on a timely basis in the  prospectus,  as
then amended or supplemented.

         (c) Promptly  after  receipt by an  Indemnified  Person or  Indemnified
Party  under  this  Section  6 of  notice  of the  commencement  of  any  action
(including any  governmental  action),  such  Indemnified  Person or Indemnified
Party  shall,  if a  Claim  in  respect  thereof  is  to  be  made  against  any
indemnifying  party under this  Section 6, deliver to the  indemnifying  party a
written notice of the commencement  thereof,  and the  indemnifying  party shall
have the right to participate in, and, to the extent the  indemnifying  party so
desires,  jointly with any other indemnifying party similarly noticed, to assume
control  of the  defense  thereof  with  counsel  mutually  satisfactory  to the
indemnifying  party and the Indemnified  Person or the Indemnified Party, as the
case may be; provided,  however, that an Indemnified Person or Indemnified Party
shall have the right to retain its own counsel  with the fees and expenses to be


                                       9
<PAGE>

paid by the  indemnifying  party,  if,  in the  reasonable  opinion  of  counsel
retained by the indemnifying  party, the  representation  by such counsel of the
Indemnified  Person or  Indemnified  Party and the  indemnifying  party would be
inappropriate  due to actual  or  potential  differing  interests  between  such
Indemnified  Person or Indemnified Party and any other party represented by such
counsel  in such  proceeding.  The  indemnifying  party  shall  pay for only one
separate legal counsel for the Indemnified  Persons or the Indemnified  Parties,
as  applicable,  and such legal counsel shall be selected by the  Investors,  as
holder of the Registrable  Securities included in the Registration  Statement to
which the Claim relates (with the approval of the  Investors),  if the Investors
are entitled to  indemnification  hereunder,  or the Company,  if the Company is
entitled to  indemnification  hereunder,  as applicable.  The failure to deliver
written  notice  to the  indemnifying  party  within  a  reasonable  time of the
commencement of any such action shall not relieve such indemnifying party of any
liability to the Indemnified  Person or Indemnified  Party under this Section 6,
except to the extent that the indemnifying  party is actually  prejudiced in its
ability to defend such action.  The  indemnification  required by this Section 6
shall be made by periodic  payments of the amount  thereof  during the course of
the  investigation  or defense,  as such expense,  loss,  damage or liability is
incurred and is due and payable.

         7. CONTRIBUTION.

         To  the  extent  any   indemnification  by  an  indemnifying  party  is
prohibited or limited by law, the indemnifying  party agrees to make the maximum
contribution  with respect to any amounts for which it would otherwise be liable
under  Section  6 hereof  to the  fullest  extent  permitted  by law;  provided,
however,  that (i) no contribution shall be made under  circumstances  where the
indemnifying  party  would not have been  liable for  indemnification  under the
fault standards set forth in Section 6, (ii) no seller of Registrable Securities
guilty of fraudulent  misrepresentation  (within the meaning of Section 11(f) of
the  Securities  Act)  shall be  entitled  to  contribution  from any  seller of
Registrable Securities who was not guilty of such fraudulent  misrepresentation,
and (iii) contribution  (together with any  indemnification or other obligations
under this Agreement) by any seller of Registrable  Securities  shall be limited
in amount to the net amount of proceeds received by such seller from the sale of
such Registrable Securities.

         8. REPORTS UNDER THE EXCHANGE ACT.


         With a view to making  available to the  Investors the benefits of Rule
144 promulgated under the Securities Act or any other similar rule or regulation
of the SEC that may at any time permit the  Investors to sell  securities of the
Company to the public without registration ("Rule 144"), the Company agrees to:

         (a) make and keep  public  information  available,  as those  terms are
understood and defined in Rule 144;

         (b)  file  with  the SEC in a  timely  manner  all  reports  and  other
documents  required of the Company under the Securities Act and the Exchange Act
so long as the Company  remains subject to such  requirements  and the filing of
such reports and other documents as is required for the applicable provisions of
Rule 144; and

         (c) furnish to the Investor,  so long as the Investor or its affiliates
owns Registrable  Securities,  promptly upon request, (i) a written statement by


                                       10
<PAGE>

the Company that it has complied  with the reporting  requirements  of Rule 144,
the  Securities  Act and the Exchange Act, (ii) a copy of the most recent annual
or quarterly report of the Company and such other reports and documents so filed
by the Company,  and (iii) such other information as may be reasonably requested
to permit the  Investor  to sell such  securities  pursuant  to Rule 144 without
registration.

         9. INFORMATION RIGHTS.

         The Company  covenants  and agrees  that,  commencing  on the date upon
which the Company ceases to file periodic reports under the Exchange Act, for so
long as the  Investors or any of their  affiliates  hold any of the  Registrable
Securities, the Company will:

         (a) Annual  Reports.  Deliver to the Investors,  as soon as practicable
and in any event  within  ninety  (90) days after the end of each fiscal year of
the Company,  audited financial  statements for the Company and its subsidiaries
for such year, setting forth in comparative form, the figures from the Company's
previous fiscal year,  prepared in accordance with generally accepted accounting
principles and practices; and

         (b) Quarterly Reports. Deliver to the Investors, as soon as practicable
and in any  event  within  forty-five  (45) days  after  the end of each  fiscal
quarter of the Company  (except the last quarter of the Company's  fiscal year),
quarterly  unaudited financial  statements on a consolidated basis,  including a
balance sheet, a statement of income and a statement of cash flows.

         10. INSPECTION RIGHTS

         The Company shall permit the Investors,  at the Investors'  expense, to
visit and inspect the Company's and its subsidiaries' properties, to examine the
books of account and records of the Company and its  subsidiaries and to discuss
the affairs,  finances and accounts of the Company and its subsidiaries with the
officers of the Company and its  subsidiaries,  all at such reasonable  times as
may be requested by the Investors;  provided,  however, that the Company and its
subsidiaries  shall not be obligated  pursuant to this Section 10 to provide the
Investors  access to any  information  which is  non-public  or they  reasonably
consider to be a trade secret or similar confidential information.

         11. ASSIGNMENT OF REGISTRATION RIGHTS.

         The  registration  rights under this  Agreement (but not the additional
rights set forth in Section 10 above,  which rights are expressly not assignable
by the  Investors)  shall be  automatically  assignable  by the Investors to any
transferee  of all  or  any  portion  of  Registrable  Securities  if:  (i)  the
transferee  agrees to execute a form of Joinder Agreement in the form of Exhibit
A attached  hereto,  and a copy of such  Joinder  Agreement  is furnished to the
Company  within a reasonable  time after such  assignment,  (ii) the Company is,
within a  reasonable  time after such  transfer or  assignment,  furnished  with
written notice of (a) the name and address of such  transferee or assignee,  and
(b) the  securities  with  respect to which such  registration  rights are being
transferred  or assigned,  (iii)  following  such  transfer or  assignment,  the
further  disposition  of  such  securities  by the  transferee  or  assignee  is
restricted  under the Securities Act and applicable  state  securities laws, and
(iv) such transferee  shall be an "accredited  investor" as that term defined in
Rule 501 of Regulation D promulgated under the Securities Act.


                                       11
<PAGE>

         12. AMENDMENT OF REGISTRATION RIGHTS.

         Provisions of this Agreement may be amended and the observance  thereof
may  be  waived  (either  generally  or  in a  particular  instance  and  either
retroactively or prospectively),  only with written consent of the Company and a
majority-in-interest  of the  Investors  (to the extent the  Investors or any of
their affiliates still own Registrable Securities);  provided,  however, that no
amendment  which  increases  the  obligations  of any  Investor  with respect to
indemnification  or contribution  shall be binding on any Investor which has not
consented  to it. Any  amendment  or waiver  effected  in  accordance  with this
Section 12 shall be binding upon the Investors and the Company.

         13. TERMINATION OF REGISTRATION RIGHTS.

         The Investors  shall not be entitled to exercise any right provided for
in Section 2 of this Agreement  after the earlier of (i) two years following the
consummation  of  the  sale  of  all  Registrable   Securities   pursuant  to  a
Registration  Statement  filed by the Company under the Securities  Act, or (ii)
such time as Rule 144(k) or another  similar  exemption under the Securities Act
is available for the sale of all of the  Investors'  shares during a three-month
period without registration.

         14. GENERAL PROVISIONS.

         (a) A  person  or  entity  is  deemed  to be a  holder  of  Registrable
Securities  whenever  such  person or entity,  or a nominee  designated  by such
person or entity,  owns of record such  Registrable  Securities.  If the Company
receives conflicting instructions, notices or elections from two or more persons
or entities with respect to the same Registrable  Securities,  the Company shall
act upon  the  basis of  instructions,  notice  or  election  received  from the
registered owner of such Registrable Securities.

         (b) Any  notices  required  or  permitted  to be given  under the terms
hereof shall be sent by certified or registered mail (return receipt  requested)
or delivered personally or by courier (including a recognized overnight delivery
service) or by facsimile and shall be effective five (5) days after being placed
in the mail,  if mailed by regular  United  States  mail,  or upon  receipt,  if
delivered  personally or by courier  (including a recognized  overnight delivery
service) or by facsimile,  in each case addressed to a party.  The addresses for
such communications shall be:

                      If to the Company:

                           Probex Corp.
                           One Galleria Tower
                           13355 Noel Road, Suite 1200
                           Dallas, Texas 75240
                           Attention:  Chief Executive Officer
                           Facsimile:  (972) 980-8545

                           With a copy to:

                           Jenkens & Gilchrist, A Professional Corporation
                           1445 Ross Avenue
                           Suite 3200
                           Dallas, Texas 75202
                           Attention: Robert W. Dockery, Esq.
                           Facsimile:  (214) 855-4300


                                       12
<PAGE>

                           If to the Investors list on Schedule B:

                           c/o Zesiger Capital Group, LLC
                           320 Park Avenue, 30th Floor
                           New York, NY 10022
                           Attention:  Albert L. Zesiger
                           Facsimile:  212-508-6329

                           With a copy to:

                           Proskauer Rose LLP
                           1585 Broadway
                           New York, NY 10036-8299
                           Attention:  Gail Sanger
                           Facsimile: 212-969-2900

                           If to any other Investor:


                           United Infrastructure Company, LLC
                           50 California Street, Suite 2200
                           San Francisco, California 94111
                           Attention:  Chief Operating Officer
                           Facsimile:  (415) 768-3491

                           With a copy to:

                           Bechtel Enterprises Holdings, Inc.
                           50 California Street, Suite 2200
                           San Francisco, California 94111
                           Attention:  Chief Counsel
                           Facsimile:  (415) 768-2233

or such other address as any party may hereafter  designate by similar notice to
the other parties hereto.

         (c)  Failure of any party to  exercise  any right or remedy  under this
Agreement or otherwise,  or delay by a party in exercising such right or remedy,
shall not operate as a waiver thereof.

         (d) This  Agreement  shall be  enforced,  governed by and  construed in
accordance  with the laws of the State of New York applicable to agreements made
and to be  performed  entirely  within  such State  excepting  its choice of law
rules,  other than Section 5-1401 of New York's General  Obligation  Law. In the
event that any provision of this Agreement is invalid or unenforceable under any
applicable  statute  or  rule  of law,  then  such  provision  shall  be  deemed
inoperative  to the extent that it may  conflict  therewith  and shall be deemed
modified to conform with such statute or rule of law. Any provision hereof which

                                       13
<PAGE>

may prove invalid or  unenforceable  under any law shall not affect the validity
or enforceability of any other provision hereof.

         (e) This Agreement, together with the Notes, the Loan Agreement and the
Intercreditor and Security Agreement, constitutes the entire agreement among the
parties  hereto  with  respect  to  the  subject  matter  hereof.  There  are no
restrictions,  promises, warranties or undertakings,  other than those set forth
or  referred to herein.  This  Agreement  supersedes  all prior  agreements  and
understandings  among the  parties  hereto with  respect to the  subject  matter
hereof,  including without limitation that certain Term Sheet dated as of August
10, 2001.

         (f)  Notwithstanding  anything  herein to the contrary,  this Agreement
shall not constitute a waiver of any of (i) United Infrastructure  Company LLC's
("UIC") rights,  the Company's  obligations or the conditions  contained in that
certain Registration and Investor Rights Agreement, Stock Purchase Agreement and
Additional Right to Purchase Agreement,  each by and between UIC and the Company
and dated as of February  2, 2001,  and (ii) the  Investors',  who are listed on
Schedule B hereto and who are parties to that certain Note Purchase Agreement by
and among the purchasers named therein,  the Company and Probex Fluids Recovery,
Inc.,  dated  as of  November  29,  2001  (the  "NPA"),  rights,  the  Company's
obligations or the conditions contained in the NPA.

         (g) Subject to the  requirements  of Section 11 hereof,  this Agreement
shall inure to the benefit of and be binding upon the  successors and assigns of
each of the parties hereto.

         (h) The headings in this  Agreement  are for  convenience  of reference
only and shall not limit or otherwise affect the meaning hereof.

         (i) This Agreement may be executed in one or more counterparts, each of
which shall be deemed an original but all of which shall  constitute one and the
same agreement.  This Agreement,  once executed by a party,  may be delivered to
the other party hereto by  facsimile  transmission  of a copy of this  Agreement
bearing the signature of the party so delivering this Agreement.

         (j) Each party shall do and perform, or cause to be done and performed,
all such further acts and things,  and shall  execute and deliver all such other
agreements,  certificates,  instruments  and  documents,  as the other party may
reasonably  request in order to carry out the intent and accomplish the purposes
of this Agreement and the consummation of the transactions contemplated hereby.









                                       14
<PAGE>


         IN WITNESS  WHEREOF,  the  Company and the  Investors  have caused this
Agreement to be duly executed as of the date first above written.

                                              PROBEX CORP.,
                                              a Delaware corporation


                                              By: /s/ Bruce A. Hall
                                                 --------------------------
                                              Name:  Bruce A. Hall
                                              Title: Senior Vice President

                                              INVESTORS LISTED ON SCHEDULE B:

                                              By: Zesiger Capital Group, LLC,
                                                  as agent and attorney-in-fact

                                                  By: /s/ Lisa W. Hess
                                                     --------------------------
                                                  Name: Lisa W. Hess
                                                  Title:   ____________________

                                              UNITED INFRASTRUCTURE COMPANY, LLC
                                              a Delaware limited liability
                                              company


                                              By: /s/ Nora A. Blum
                                                 -----------------------------
                                                 Nora A. Blum
                                                 Vice President




                        SCHEDULES INTENTIONALLY OMITTED.



                                       15
<PAGE>
                                    Exhibit A


                  Form of Registration Rights Joinder Agreement



Probex Corp.
13355 Noel Road, Suite 1200
Dallas, Texas 75240

Attention:  Secretary

Ladies & Gentlemen:

         In  consideration  of the transfer to the  undersigned of  ____________
shares of the common stock of Probex Corp.,  a corporation  organized  under the
laws of the State of Delaware (the "Company"),  the undersigned  represents that
[he][she][it]  is a permitted  transferee  of [insert  name of  transferor]  and
agrees that, as of the date written  below,  [he][she][it]  shall become a party
to, and an Investor as defined in that certain  Registration  Rights  Agreement,
dated as of September 7, 2001, as such agreement may have been amended from time
to time (the "Agreement"),  between the Company and the Investors named therein,
and shall be fully  bound by, and subject  to, all of the  covenants,  terms and
conditions of the Agreement, as though a party thereto.

                     Executed as of the ____ day of __________, ______ .


                      SIGNATORY:_______________________

                      Address:___________________________

                              ____________________________


                      ACKNOWLEDGED AND ACCEPTED:

                         PROBEX CORP.

                         By: _________________________
                         Name:_______________________
                         Title:________________________













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