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                                                                 EXHIBIT 10.20.2




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                          REGISTRATION RIGHTS AGREEMENT



                          DATED AS OF OCTOBER 12, 2000



                                 BY AND BETWEEN



                                  PROBEX CORP.



                                       AND



                       UNITED INFRASTRUCTURE COMPANY, LLC







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                                TABLE OF CONTENTS

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<S>                                                                                                            <C>
1.       DEFINITIONS..............................................................................................1

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

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

4.       OBLIGATIONS OF THE INVESTORS.............................................................................8

5.       EXPENSES OF REGISTRATION.................................................................................9

6.       INDEMNIFICATION..........................................................................................9

7.       CONTRIBUTION............................................................................................11

8.       REPORTS UNDER THE EXCHANGE ACT..........................................................................11

9.       ASSIGNMENT OF REGISTRATION RIGHTS.......................................................................12

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

11.      MISCELLANEOUS...........................................................................................12
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                          REGISTRATION RIGHTS AGREEMENT


         REGISTRATION RIGHTS AGREEMENT (this "Agreement"), dated as of October
12, 2000, by and between Probex Corp., a Delaware corporation, with its
headquarters located at 13355 Noel Road, Suite 1200, Dallas, TX 75240 (the
"Company"), and United Infrastructure Company, LLC, a Delaware limited liability
company (together with its respective affiliates, any assignee or transferee of
all of its respective rights hereunder, the "Initial Investor").

         WHEREAS, in connection with the Stock Purchase Agreement by and between
the parties hereto of even date herewith (the "Stock Purchase Agreement"), the
Company has agreed, upon the terms and subject to the conditions contained
therein, to issue and sell to the Initial Investor shares of its common stock,
par value $.001 per share (the "Common Stock").

         WHEREAS, to induce the Initial Investor to execute and deliver the
Stock Purchase Agreement, the Company has agreed to provide 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 pursuant to this
Agreement.

         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
Initial Investor hereby agree as follows:

     1.   DEFINITIONS.

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

                  (i) "Investor(s)" means the Initial Investor and any
          transferee or assignee who agrees to become bound by the provisions of
          this Agreement in accordance with Section 9 hereof and executes a form
          of Joinder Agreement attached hereto as Exhibit A.

                  (ii) "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").

                  (iii) "Registrable Securities" means the Common Shares, the
          Additional Common Shares, if any, and any shares of capital stock
          issued or issuable as a dividend on or in exchange for or otherwise
          with respect to any of the foregoing.


<PAGE>   4

                  (iv) "Registration Statement" means a registration statement
          of the Company under the Securities Act.

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

     2.   REGISTRATION.

          (a) Mandatory Registration. The Company shall prepare, and, on or
prior to the date which is 60 days after the Closing Date, file with the SEC 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, subject
to the consent of the Initial Investor, which consent will not be unreasonably
withheld) covering the resale of the Registrable Securities issued pursuant to
the Stock Purchase Agreement to enable the resale by the Initial Investor from
time to time on the American Stock Exchange (the "AMEX") or in
privately-negotiated transactions.

          (b) Payments by the Company. The Company shall use its best efforts to
obtain effectiveness of the Registration Statement as soon as practicable. If
(i) the Registration Statement(s) covering the Registrable Securities required
to be filed by the Company pursuant to Section 2(a) hereof is not declared
effective by the SEC by January 31, 2001 or if, after the Registration Statement
has been declared effective by the SEC, sales cannot be made pursuant to the
Registration Statement, or (ii) the Common Stock and Common Shares are not
listed on the AMEX after being so listed, then the Company shall make payments
to Investors in such amounts and at such times in the manner set forth below as
partial relief for the damages to Investors by reason of any such delay in or
reduction of their ability to sell the Registrable Securities (which remedy
shall not be exclusive of any other remedies available at law or in equity):

                  (i) each Investor shall be entitled to receive additional
          shares of Common Stock in the amount of 5% of the Common Shares
          purchased by such Investor under the Stock Purchase Agreement;

                  (ii) If the Registration Statement(s) covering the Registrable
          Securities required to be filed by the Company pursuant Section 2(a)
          hereof is not declared effective by the SEC on or before January 31,
          2001, each Investor shall be entitled to receive additional shares of
          Common Stock in the amount of 7.5% of the Common Shares purchased by
          such Investor under the Stock Purchase Agreement for each additional
          30-day period thereafter, until the earlier of: (a) the date on which
          the Registration Statement is declared effective by the SEC or (b)
          March 31, 2001;

                  (iii) If the Registration Statement(s) covering the
          Registrable Securities required to be filed by the Company pursuant
          Section 2(a) hereof is not declared effective by the SEC on or before
          March 31, 2001, the Initial Investor shall be entitled to demand
          registration rights as set forth in that certain Stock Purchase Term
          Sheet of even date herewith;



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provided, however, that the dates on which damages payments are incurred by the
Company pursuant to this Section 2(b) shall be extended by the Dispute Delay(s)
(as defined in Section 3(g)).

          (c) Piggy-Back Registrations. Subject to the last sentence of this
Section 2(c), if at any time prior to the expiration of the Registration Period
(as hereinafter defined) 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 each Investor written notice of such
determination and, if within fifteen (15) days after the effective date of such
notice, such Investor shall so request in writing, the Company shall include in
such Registration Statement all or any part of the Registrable Securities such
Investor requests 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 such Investor has requested
inclusion hereunder as the underwriter shall permit. Any exclusion of
Registrable Securities shall be made pro rata among Investors seeking to include
Registrable Securities in proportion to the number of Registrable Securities
sought to be included by Investors; 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(c) shall be
construed to limit any registration required under Section 2(a) hereof. If an
offering in which Investors are entitled to registration under this Section 2(c)
is an underwritten offering, then each Investor 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. Notwithstanding anything to the contrary
set forth herein, the registration rights of Investors pursuant to this Section
2(c) 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.

     3.   OBLIGATIONS OF THE COMPANY.

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



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          (a) The Company shall prepare promptly, and file with the SEC not
later than 60 days after the Closing Date, a Registration Statement with respect
to the number of Registrable Securities provided in Section 2(a), and thereafter
use its best efforts to cause such Registration Statement relating to
Registrable Securities 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 and (ii) the date on which the Registrable
Securities (in the opinion of counsel to the Initial Investors) 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 each Investor whose Registrable
Securities are included in the Registration Statement and 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
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 of any thereof which contains information for which the Company
has sought confidential treatment), and (ii) such number of copies of a
prospectus, including a preliminary prospectus, and all amendments and
supplements thereto and such other documents as such Investor may reasonably
request in order to facilitate the disposition of the Registrable Securities
owned by such Investor. The Company will promptly notify each Investor 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 who hold a majority in interest of the Registrable Securities
being offered reasonably request, (ii) prepare and file in



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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 each Investor 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 each Investor as such Investor 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 each Investor who holds 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 a single firm of counsel designated by
Investors who hold a majority in interest 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 not file any document in
a form to which such counsel reasonably objects and will not request
acceleration of the Registration Statement without prior notice to such counsel.
In the event of a disagreement between Investors and the Company regarding any
action taken by the Company to which counsel to Investors objects (the
"Dispute"), Investors shall give written notice (the "Dispute Notice") of the
Dispute to the Company delivered in accordance with Section 11(b) of this
Agreement. The Dispute Notice shall set forth in reasonable detail the Dispute
of Investors. Upon receipt of the Dispute Notice, the dates upon which the
Company incurs damage payments to Investors ("Damages Dates"), set forth in
Section 2(b), including subsections thereof, of this Agreement, shall be
extended by the number of elapsed day(s) of the Dispute (the "Dispute Delay") .
Upon written notice to the Company by Investors of a resolution (the "Resolution
Notice") of the Dispute to the satisfaction of Investors, the Damage Dates shall
be adjusted by the Dispute Delay upon of receipt by the Company of the
Resolution Notice delivered in accordance with Section 11(b) of this Agreement.
The sections of the Registration Statement covering information with respect to
Investors, Investors' beneficial ownership of securities of



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the Company or Investors intended method of disposition of Registrable
Securities shall conform to the information provided to the Company by each
Investor.

          (h) The Company shall make generally available to its security holders
as soon as practical, but not later than ninety (90) days after the close of the
period covered thereby, an earnings statement (in form complying with the
provisions of Rule 158 under the Securities Act) covering a twelve-month period
beginning not later than the first day of the Company's fiscal quarter next
following the effective date of the Registration Statement.

          (i) At the request of any Investor, 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 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
Investors.

          (j) The Company shall make available for inspection by (i) 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 Investors, and (iv) one firm of attorneys retained
by 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 an Investor) 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 agreements (in
form and substance satisfactory to the Company) with the Company with respect
thereto, substantially in the form of this Section 3(j). Each Investor agrees
that it 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 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 any Investor) shall be deemed
to limit Investors' ability to sell Registrable Securities in a manner which is
otherwise consistent with applicable laws and regulations.



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          (k) The Company shall hold in confidence and not make any disclosure
of information concerning an Investor 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 an
Investor is sought in or by a court or governmental body of competent
jurisdiction or through other means, give prompt notice to such Investor prior
to making such disclosure, and allow 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 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 Investors who hold 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 Investors may reasonably request and registered in
such names as the managing underwriter or underwriters, if any, or 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
Investors whose Registrable Securities are included in such Registration
Statement) an instruction in customary form and substance and an opinion of such
counsel in customary form and substance.

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



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          (p) In the event that Investors transfer or assign any Registrable
Securities, in accordance with Section 9, 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 Investors of Registrable Securities
pursuant to the Registration Statement.

     4.   OBLIGATIONS OF INVESTORS.

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

          (a) It shall be a condition precedent to the obligations of the
Company to complete the registration pursuant to this Agreement with respect to
the Registrable Securities of a particular Investor that such Investor shall
furnish to the Company such information regarding itself, the Registrable
Securities held by it and the intended method of disposition of the Registrable
Securities held by it 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 each Investor of the information the Company
requires from each such Investor.

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

          (c) Each Investor agrees that, upon receipt of any notice from the
Company of the happening of any event of the kind described in Section 3(e) or
3(f), such Investor will immediately discontinue disposition of Registrable
Securities pursuant to the Registration Statement covering such Registrable
Securities until such Investor's receipt of the copies of the supplemented or
amended prospectus contemplated by Section 3(e) or 3(f) and, if so directed by
the Company, such Investor 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 such Investor's possession, of the prospectus covering such
Registrable Securities current at the time of receipt of such notice.

          (d) No Investor may participate in any underwritten registration
hereunder unless such Investor (i) agrees to sell such Investor's 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 reasonably required under the terms of such underwriting
arrangements, and (iii) agrees to pay its pro rata share of all underwriting
discounts and



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commissions and any expenses in excess of those payable by the Company pursuant
to Section 5 below.

     5.   EXPENSES OF REGISTRATION.

     All reasonable expenses, other than underwriting discounts and commissions,
incurred in connection with registrations, filings or qualifications pursuant to
Sections 2 and 3, 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 pursuant to Section 3(g) hereof 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) each Investor who holds such Registrable Securities,
(ii) the directors, officers, partners, employees, agents and each person who
controls any Investor within the meaning of the Securities Act or the Securities
Exchange Act of 1934, as amended (the "Exchange Act"), if any, (iii) any
underwriter (as defined in the Securities Act) for the Investors, 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) 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



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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) 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 Investors pursuant to Section 9.

          (b) In connection with any Registration Statement in which an Investor
is participating, each such Investor agrees 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), 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 stockholder selling securities pursuant to the
Registration Statement or any of its directors or officers or any person who
controls such 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 such 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 such Investor
furnished to the Company by such Investor expressly for use in connection with
such Registration Statement; and subject to Section 6(c) such 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 such 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) for only that amount as
does not exceed the net proceeds to such 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 Investors pursuant to Section 9. 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



                                       10
<PAGE>   13
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 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 Investors holding a majority-in-interest of the Registrable
Securities included in the Registration Statement to which the Claim relates
(with the approval of the Initial Investor), 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 to the fullest extent permitted by law; provided, however, that (i) no
contribution shall be made under circumstances where the maker 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:



                                       11
<PAGE>   14

          (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 (it being understood
that nothing herein shall limit the Company's obligations under the Stock
Purchase Agreement) and the filing of such reports and other documents is
required for the applicable provisions of Rule 144; and

          (c) furnish to each Investor so long as such Investor owns Registrable
Securities, promptly upon request, (i) a written statement by 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
Investors to sell such securities pursuant to Rule 144 without registration.

     9.   ASSIGNMENT OF REGISTRATION RIGHTS.

     The rights under this Agreement 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 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, (iv)
such transfer shall have been made in accordance with the applicable
requirements of the Stock Purchase Agreement, and (v) such transferee shall be
an "accredited investor" as that term defined in Rule 501 of Regulation D
promulgated under the Securities Act.

     10.  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, the Initial
Investor (to the extent the Initial Investor still owns Registrable Securities)
and the Investors who hold a majority-in-interest of the Registrable Securities.
Any amendment or waiver effected in accordance with this Section 10 shall be
binding upon each Investor and the Company.

     11.  MISCELLANEOUS.

          (a) A person or entity is deemed to be a holder of Registrable
Securities whenever 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.



                                       12
<PAGE>   15

          (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 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, TX  75240
                           Attention:  Chief Executive Officer
                           Facsimile:  (972) 980-8545

                           With a copy to:

                           Jenkens & Gilchrist
                           a professional corporation
                           1445 Ross Avenue, Suite 3200
                           Dallas, TX  75202
                           Attention:  Robert W. Dockery, Esq.
                           Facsimile:  (214) 855-4300

                           If to the Initial Investor:

                           United Infrastructure Company, LLC
                           50 California Street, Suite 2200
                           San Francisco, CA  94111
                           Attention:  Chief Operating Officer
                           Facsimile:  (415) 768-1714

                           With a copy to:

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


          (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.



                                       13
<PAGE>   16

          (d) This Agreement shall be enforced, governed by and construed in
accordance with the laws of the State of Texas applicable to agreements made and
to be performed entirely within such State. 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 may prove invalid or unenforceable
under any law shall not affect the validity or enforceability of any other
provision hereof. The parties hereto hereby submit to the exclusive jurisdiction
of the United States federal courts located in Dallas, Texas with respect to any
dispute arising under this Agreement or the transactions contemplated hereby.

          (e) This Agreement and the Stock Purchase Agreement (including all
schedules and exhibits thereto) constitute the entire agreement among the
parties hereto with respect to the subject matter hereof and thereof. There are
no restrictions, promises, warranties or undertakings, other than those set
forth or referred to herein and therein. This Agreement and the Stock Purchase
Agreement supersede all prior agreements and understandings among the parties
hereto with respect to the subject matter hereof and thereof.

          (f) Subject to the requirements of Section 9 hereof, this Agreement
shall inure to the benefit of and be binding upon the successors and assigns of
each of the parties hereto.

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

          (h) This Agreement may be executed in two 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.

          (i) 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.

          (j) Except as otherwise provided herein, all consents and other
determinations to be made by the Investors pursuant to this Agreement shall be
made by Investors holding a majority of the Registrable Securities.

          (k) The language used in this Agreement will be deemed to be the
language chosen by the parties to express their mutual intent, and no rules of
strict construction will be applied against any party.



                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]


                                       14
<PAGE>   17


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

                                   PROBEX CORP.



                                   By: /s/ D. YALE SAGE
                                       ------------------------------------
                                   Name:   D. Yale Sage
                                   Title:  Vice President





                                   UNITED INFRASTRUCTURE COMPANY, LLC



                                   By: /s/ NORA A. BLUM
                                       ------------------------------------
                                   Name:   Nora A. Blum
                                   Title:  Authorized Person


<PAGE>   18



                                                                       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
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
October 12, 2000, as such agreement may have been amended from time to time (the
"Agreement"), between the Company and United Infrastructure Company, LLC, a
Delaware limited liability company, 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:
                                           ------------------------------------