Document:

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                                                                  Exhibit 10.7.3

                  SECOND AMENDMENT TO STOCK RIGHTS AGREEMENT

          THIS SECOND AMENDMENT TO STOCK RIGHTS AGREEMENT (this "Amendment") is
made as of this 4th day of February 2000 by and among Timothy J. Bancroft (the
"Stockholder"), PaeTec Corp., a Delaware corporation (the "Company"), PaeTec
Communications, Inc., a Delaware corporation and wholly-owned subsidiary of the
Company (the "Subsidiary"), and Arunas A. Chesonis ("Mr. Chesonis").

                                    RECITALS
                                    --------

          A.  The Company, the Subsidiary, the Stockholder and Mr. Chesonis are
parties to a Stock Rights Agreement dated as of August 30, 1998 (the "Stock
Rights Agreement") and amended as of September 30, 1998 ("Amendment No. 1").

          B.  The Board of Directors of the Company has authorized the issuance
and sale (the "Series A Preferred Stock Placement") of 134,000 shares of a new
series of preferred stock of the Company, designated the Series A Convertible
Preferred Stock, to the purchasers (the "Purchasers") listed on the Schedule of
Purchasers to, and pursuant to the terms and conditions of, an Equity Purchase
Agreement (the "Purchase Agreement").

          C.  As a condition to the consummation of the Series A Preferred Stock
Placement, the Purchasers have required that the Company, the Subsidiary, the
Stockholder and Mr. Chesonis further amend the Stock Rights Agreement (i) to
provide that all Class B Shares (as defined in the Stock Rights Agreement) shall
automatically convert into shares of Class A common stock, par value $0.01 per
share ("Class A Common Stock"), of the Company in specified circumstances and
(ii) to clarify that to the extent any securities are required to be excluded
from a registration pursuant to the "cut-back" provisions of the piggyback
registration rights granted to the Stockholder pursuant to the Stock Rights
Agreement, the securities to be included in such registration shall be
determined on a pro rata basis among the holders of shares participating in the
                --- ----
offering pursuant to registration rights granted by the Company, based on the
number of shares of common stock requested to be included by each such holder in
such registration.

          D.  The parties to the Stock Rights Agreement desire to amend the
Stock Rights Agreement to induce the Purchasers to consummate of the Series A
Preferred Stock Placement.
<PAGE>

                                   AGREEMENT
                                   ---------

          1.  Defined Terms.  All capitalized terms used in this Amendment
              -------------
without definition shall have the meanings given to such terms in the Stock
Rights Agreement, as amended.

          2.  Automatic Conversion of Class B Shares.  Notwithstanding
              --------------------------------------
anything in the Stock Rights Agreement or Amendment No. 1 to the contrary, the
parties agree that, as provided in the Company's certificate of incorporation as
amended in connection with the Series A Preferred Stock Placement (the "Restated
Certificate of Incorporation"), each Class B Share subject to the Stock Rights
Agreement (as amended) shall automatically convert into one share of Class A
Common Stock upon the date (the "Termination Date") that the Stockholder ceases
to be employed by the Company or any subsidiary thereof unless, at the
Termination Date, Mr. Chesonis shall (i) be the Chairman of the Board or Chief
Executive Officer of the Company, (ii) be the beneficial owner of shares of
Class B common stock of the Company and (iii) have the power pursuant to a proxy
to vote the Class B Shares on all matters on which such Class B Shares are
entitled to vote, provided Mr. Chesonis personally exercises such power and does
not delegate the exercise thereof to any other person.  If subsequent to the
Termination Date, any condition specified in clause (i), (ii) or (iii) in the
preceding sentence shall cease to be in effect, each Class B Share shall
immediately be converted into one share of Class A Common Stock.  All other
terms and conditions of the Stock Rights Agreement, as amended, shall continue
to apply to such shares of Class A Common Stock upon such conversion.  In the
event of any conflict between the provisions of this Section 2 and the
provisions of Article V of the Restated Certificate of Incorporation with
respect to such mandatory conversion, which shall include, without limitation,
any additional mandatory conversion events specified in such Article V, the
provisions of Article V of the Restated Certificate of Incorporation shall
control.

          3.  Amendment of Section 6(b).  The fourth and fifth sentences of
              -------------------------
Section 10(b) of the Stock Rights Agreement are hereby deleted and replaced and
superseded in their entirety with the following sentence:

     "Notwithstanding any other provision of this Section 6, if the managing
     underwriter advises in writing the Company and the Stockholder that
     marketing factors require a limitation of the number of shares of common
     stock to be underwritten and sold in such offering, the managing
     underwriter may exclude some or all of the shares of common stock to be
     sold in such offering from such registration, and the shares to be included
     in such registration shall be allocated pro rata among the holders of
                                             --- ----
     shares participating in the offering pursuant to registration rights
     granted by the Company (including demand and piggyback registration
     rights), based on the number of shares of

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     common stock requested to be included by each holder in such registration."

          4.  Binding Effect.  This Amendment shall be binding upon and inure to
              --------------
the benefit of the parties hereto and their heirs, executors, administrators,
successors and assigns.

          5.  Governing Law.  This Amendment shall be governed by, and construed
              -------------
and enforced in accordance with, the laws of the State of New York, except that
if any provision of this Amendment or any part of any such provision would be
illegal, invalid or enforceable under such laws in connection with a suit or
proceeding validly instituted in another jurisdiction, then the laws of such
other jurisdiction shall govern insofar as is necessary to sustain the legality,
validity or enforceability of such provision or any part of such provision.

          6.  Captions.  Captions to the Sections in this Amendment are for the
              --------
convenience of the parties only and shall not affect the meaning or
interpretation of this Amendment.

          7.  Enforceability and Interpretation.  It is the intention of the
              ---------------------------------
parties to this Amendment that the terms and provisions contained in this
Amendment shall be enforceable to the fullest extent permitted by law.  If any
term or provision of this Amendment or the application thereof to any Person or
circumstance is construed to be illegal, invalid or unenforceable, in whole or
in part, then such term or provision shall be construed in such a manner as to
permit its enforceability under applicable law to the fullest extent permitted
by such law.  In any case, the remaining terms and provisions of this Amendment
or the application thereof to any Person or circumstance, except those terms and
provisions which have been held illegal, invalid or unenforceable, shall remain
in full force and effect.

          8.  Counterparts.  This Amendment may be executed in one or more
              ------------
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

          9.  Additional Documents.  Each party hereto agrees to execute any and
              --------------------
all documents, instruments, certificates and communications deemed to be
necessary or advisable by the Company to effectuate the purposes of this
Amendment.

                           [signature page follows]

                                       3
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          IN WITNESS WHEREOF, the parties hereto have executed and delivered
this Amendment with full force and effect as of the day and year first written
above.

                            PAETEC CORP.

                            By:   /s/ Aruna A. Chesonis
                                 --------------------------------
                            Its:   CEO, Chairman and President
                                 --------------------------------

                            PAETEC COMMUNICATIONS, INC.

                            By:   /s/ Aruna A. Chesonis
                                 --------------------------------
                            Its:   CEO, Chairman and President
                                 --------------------------------

                              /s/ Aruna A. Chesonis
                            -------------------------------------
                            Arunas A. Chesonis

                              /s/ Timothy J. Bancroft
                            -------------------------------------
                            Timothy J. Bancroft

                                       4<PAGE>

                                                                  Exhibit 10.8.1

                            STOCK RIGHTS AGREEMENT

          This is a Stock Rights Agreement (the "Agreement"), dated July 17,
1998, between JOHN BARON ("Shareholder"), PAETEC CORP., a Delaware corporation
with its principal place of business at 290 Woodcliff Drive, Fairport, New York
14450 (the "Company"), PAETEC COMMUNICATIONS, INC., a Delaware corporation and
wholly-owned subsidiary of the Company with its principal place of business at
290 Woodcliff Drive, Fairport, New York 14450 ("Subsidiary"), and ARUNAS A.
CHESONIS ("Founder").

                                   RECITALS

          A.  The Company is a Delaware corporation having 110,000,000 shares of
authorized capital stock, 10,000,000 of which are designated preferred stock,
75,000,000 of which are designated Class A common and 25,000,000 of which are
designated Class B common.  Founder is one of the founding shareholders of the
Company.

          B.  Shareholder is also one of the founding Shareholders of the
Company and is an employee of the Subsidiary.  In order to induce Shareholder to
leave his former employer and join the Subsidiary as an employee, the Company
previously offered to issue to Shareholder 250,000 shares of Class A common
stock at a purchase price of $.40 per share, subject to certain restrictions.

          C.  The Company, Subsidiary, Shareholder, and Founder enter into this
Agreement for the purpose of confirming Shareholder's equity interest in the
Company and outlining the rights of and restrictions imposed by the Company with
respect to the shares of stock held by the Shareholder.

          NOW, THEREFORE, in consideration of the following mutual promises, the
parties agree as follows:

          1.  Issuance of Shares.
              ------------------

          (a) The Company confirms its previous offer to issue 250,000 shares of
Class A common stock (the "Shares") to Shareholder at a price of $.40 per share
payable in full upon issuance of the Shares.  A stock certificate evidencing the
Shares shall be issued in the name of Shareholder upon receipt of this executed
Agreement and payment in full of the purchase price.

          (b) In order to induce the Company to issue the Shares, Shareholder
represents and warrants to the Company as follows:
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               (i)   Shareholder (A) understands that an investment in the
Shares is speculative due to factors including (but not limited to) the start-up
nature of the Company and the risk of economic loss from the operations of the
Company, but believes that such an investment is suitable for Shareholder based
upon Shareholder's financial needs, (B) can withstand a complete loss of the
investment in the Shares, and (C) has the net worth to undertake these risks.

               (ii)  Shareholder is acquiring the Shares for the personal
account of Shareholder, with no present intention of reselling, distributing or
otherwise transferring the Shares or any portion of the Shares to anyone else.

               (iii) Shareholder understands and acknowledges that the Shares
are being offered and sold under one or more exemptions provided in the
Securities Act of 1933, as amended (the "Securities Act"), Regulation D
promulgated thereunder and applicable New York State securities laws, and that
this transaction has not been reviewed or passed upon by the United States
Securities and Exchange Commission, the New York State Attorney General, or any
other federal or state agency.

               (iv)  Shareholder realizes that Shareholder must bear the
economic risk of investment for an indefinite period of time because (A) the
Shares have not been registered under the Securities Act and cannot be resold by
Shareholder unless they are subsequently registered under the Securities Act or
an exemption from registration is available, (B) the transferability of the
Shares is restricted by the terms of this Agreement, and (C) there currently is
no public market for the Shares, and Shareholder may not be able to liquidate
the investment in the Shares in the event of an emergency. Shareholder has
adequate means of providing for Shareholder's current financial needs and
personal contingencies, and has no need for liquidity of investment with respect
to the Shares.

               (v)   Shareholder believes that Shareholder, either alone or
together with the assistance of professional advisor(s), has knowledge and
experience in business and financial matters sufficient to make Shareholder
capable of evaluating the merits and risks of an investment in the Shares.

               (vi)  Shareholder is fully familiar with the business of the
Company and its present and proposed operations. Shareholder has been given
reasonable opportunity to ask representatives of the Company questions
concerning the Company and making an investment in the Shares. Shareholder has
obtained sufficient information to evaluate the merits and risks of an
investment in the Shares.

               (vii) Shareholder confirms that Shareholder has been advised to
rely on professional accounting, tax, legal and financial advisers with respect
to an investment in the Shares and has obtained, to the extent Shareholder deems
it necessary, professional advice

                                       2
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with respect to the risks inherent in an investment in the Shares and the
suitability of an investment in the Shares in light of Shareholder's financial
condition and investment needs.

          2.  Restriction on Transfer of Shares.  Shareholder may not sell,
              ---------------------------------
transfer, pledge, assign, transfer, or otherwise encumber or dispose of, in any
manner or by any means, any Shares that are subject to the Company's Purchase
Option described in Section 3 of this Agreement.  This restriction on transfer
does not apply to any Shares that, pursuant to Section 3, no longer are subject
to the Company's Purchase Option or to any additional shares of capital stock of
the Company that Shareholder might acquire in the future.  Notwithstanding the
foregoing, Shareholder may pledge the Shares to Founder as collateral security
for a promissory note dated the date hereof, provided that the Shares so pledged
shall continue to be subject to the Company's Purchase Option described in
Section 3 below.

          3.  Repurchase of Shares upon Termination of Employment with
              --------------------------------------------------------
Subsidiary.  Upon termination of Shareholder's employment with the Subsidiary,
----------
the Company shall have an option, but shall not be obligated, to repurchase (the
"Purchase Option") from Shareholder or Shareholder's personal representative all
or a portion of Shareholder's Shares, as set forth in the following
subparagraphs.

          (a) If Shareholder's employment with the Subsidiary terminates due to
voluntary separation or dismissal for Cause (as defined below), the number of
Shares that are subject to the Company's Purchase Option shall be determined as
follows:

              (i)   The Company shall have the option to repurchase up to 100%
of the Shares should Shareholder's employment terminate at any time prior to the
first anniversary of Shareholder's employment with the Subsidiary.

              (ii)  The Company shall have the option to repurchase up to 60% of
the Shares should Shareholder's employment terminate on the first anniversary
date, or at any time between the first and second anniversary dates, of
Shareholder's employment with the Subsidiary.

              (iii) The Company shall have the option to repurchase up to 40% of
the Shares should Shareholder's employment terminate on the second anniversary
date, or at any time between the second and third anniversary dates, of
Shareholder's employment with the Subsidiary.

              (iv)  The Company shall have the option to repurchase up to 20% of
the Shares should Shareholder's employment terminate on the third anniversary
date, or at any time between the third and fourth anniversary dates, of
Shareholder's employment with the Subsidiary.

                                       3
<PAGE>

          (b) If Shareholder's employment with the Subsidiary terminates because
of Shareholder's death or disability, Shareholder or Shareholder's personal
representative may negotiate a transfer of all or a portion of Shareholder's
Shares back to the Company at any time.  With respect to Shares that were
subject to the Company's Purchase Option and that are not transferred back to
the Company, the transfer restrictions set forth in Section 2 above shall apply
to the same extent that they would have applied if Shareholder's employment had
continued.  This restriction on transfer does not apply to any Shares that would
no longer have been subject to the Company's Purchase Option, or to any
additional shares of capital stock of the Company that Shareholder might acquire
in the future.

          (c) In the event that Shareholder's employment with the Subsidiary
terminates for any reason not addressed in subparagraphs (a) and (b) above, the
Company's Purchase Option, together with all transfer restrictions set forth in
Section 2, shall fully expire effective as of the date of termination.

          (d) The Company's Purchase Option shall fully expire on the fourth
anniversary of Shareholder's employment with the Subsidiary.   Shares as to
which the Company's Purchase Option has expired are no longer subject to the
transfer restrictions set forth in Section 2.

          (e) To exercise its Purchase Option, the Company must notify
Shareholder or Shareholder's personal representative of its intention to
exercise its Purchase Option within 60 days after the date of termination of
Shareholder's employment with the Subsidiary.  Should the Company fail to
exercise the Purchase Option within such 60-day period, the Shares shall no
longer be subject to the transfer restrictions set forth in Section 2.

          (f) In the event of a consolidation or merger of the Company with or
into any other person or entity, a sale of all or substantially all of the
assets of the Company to another person or entity, or an acquisition of more
than 50% of the capital stock of the Company by another person or entity, the
Company's Purchase Option shall be terminated as of the effective date of the
transfer.  Notwithstanding the foregoing, the Company's Purchase Option shall
not be terminated or in any other way affected by an initial public offering of
stock by the Company.

          4.  Repurchase Price and Payment Terms.  The price for all Shares
              ----------------------------------
purchased by the Company pursuant to the Purchase Option shall be $.40 per
Share.  Payment shall be made in full for all repurchased Shares within 30 days
after the date on which the Company delivers notice of its intention to exercise
the Purchase Option.  Upon payment, Shareholder or Shareholder's personal
representative shall deliver all stock certificates for repurchased Shares,
properly endorsed in blank, to the Company or its designee.

                                       4
<PAGE>

          5.  Non-Competition.
              ---------------

          (a) For a period of one year after termination of Shareholder's
employment with the Subsidiary (regardless of the reason for termination),
Shareholder shall not, directly or indirectly:

              (i)   solicit or serve clients or customers of the Company or any
affiliate of the Company (including the Subsidiary), whether for Shareholder's
own account or as an employee, shareholder, partner, officer, member, manager,
director, consultant, or other representative of any third party;

              (ii)  direct any business from, or enter into competition with,
the Company or any affiliate of the Company (including the Subsidiary) in any
line of business in which the Company or such affiliate was conducting
operations during Shareholder's employment; or

              (iii) serve as an employee, shareholder, partner, officer, member,
manager, director, consultant or other representative of any third party which
engages in any line of business competitive with the Company or any affiliate of
the Company (including the Subsidiary) anywhere in the world.

Shareholder acknowledges that the foregoing limitations are reasonable in time
and scope and agrees not to raise any objection to the reasonableness of the
foregoing in any action or proceeding to enforce the terms of this Section.

          (b) As consideration for the non-competition covenant set forth in
subparagraph (a) above, the Subsidiary agrees that, if Shareholder's employment
is terminated by the Subsidiary without Cause, Subsidiary shall pay Shareholder
or Shareholder's personal representative during the one-year period in which the
covenant is in effect an amount equal to the annualized base salary paid to
Shareholder immediately prior to termination of Shareholder's employment.
Payment shall be made in accordance with the Subsidiary's customary payroll
practices.  Continued payment of Shareholder's base salary under this
subparagraph (b) shall not be made if termination of Shareholder's employment is
due to Shareholder's death, disability, voluntary resignation or withdrawal or
termination for "Cause" (as defined below).

          (c) As additional consideration for the non-competition covenant set
forth in subparagraph (a) above, the Company agrees that (i) in the event
Shareholder's employment terminates due to the death or disability of
Shareholder or is terminated by Subsidiary without Cause, the one-year period
during which the non-competition covenant is to be in effect shall be counted as
a year of employment with Subsidiary for purposes of determining the percentage
of Shares that is subject to the Company's Purchase Option, and (ii) in the
event Shareholder's employment is terminated by the Subsidiary for Cause or
terminates due to the

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<PAGE>

voluntary resignation or withdrawal of Shareholder, the Company shall have the
option of (A) waiving the non-competition covenant set forth in subparagraph (a)
above or (B) counting the one-year period during which the non-competition
covenant is to be in effect as a year of employment for purposes of determining
the percentage of Shares that is subject to the Company's Purchase Option.

          (d)  (i)  Should Shareholder violate the terms of the non-competition
covenant set forth in subparagraph (a), the Company, the Company shall notify
Shareholder in writing of the alleged violation that constitutes a breach of
this Agreement, and Shareholder shall have 10 business days to cure the breach.
If the breach is not cured to the satisfaction of the Company, then in addition
to any other remedies available under law, the Company may (1) discontinue any
payments being made to Shareholder pursuant to subparagraph (b) hereof, and (2)
exercise its Purchase Option with respect to any additional Shares that would
have been subject to the Purchase Option had the one-year period of the non-
competition covenant not been counted as an additional year of employment
pursuant to the terms of subparagraph (c) hereof.  Exercise of the Purchase
Option with respect to such additional Shares shall be made in accordance with
the terms of Sections 3 and 4 hereof, except that the Company may exercise the
Purchase Option at any time within 60 days after the Company first becomes aware
of Shareholder's violation of subparagraph (a).

               (ii) In the event that the Company fails to make any payment due
to Shareholder pursuant to Section 5(b) above, Shareholder shall notify the
Company in writing of the alleged failure to make payment that constitutes a
breach of this Agreement, and the Company shall have 5 business days to cure the
breach. If the breach is not cured to the satisfaction of Shareholder, then the
non-competition covenant set forth in subparagraph (a) shall be null and void
and of no further force and effect.

          (e)  For purposes of this Section 5, termination for "Cause" shall
mean termination of Shareholder's employment with the Subsidiary due to: (i)
material failure or refusal to perform the duties assigned to Shareholder, (ii)
refusal of Shareholder to follow the reasonable directives of the Board of
Directors or Chief Executive Officer of the Subsidiary, (iii) conviction of a
felony, (iv) misappropriation of any funds or property of the Company or any
affiliate of the Company (including the Subsidiary), or (v) commission of any
act which could materially injure the business or reputation of, or materially
adversely affect the interests of Company or any affiliate of the Company
(including the Subsidiary).

          (f)  Shareholder acknowledges that his/her services are unique and
extraordinary and are not readily replaceable, and hereby expressly agrees that,
in the event of a violation of the non-competition covenant set forth in
subparagraph (a), the Company and its affiliates (including Subsidiary) will be
irreparably harmed and the remedy of damages or other remedy at law will be
inadequate.  Therefore, Shareholder agrees that, in the event of a threatened or
actual violation of the non-competition covenant, the Company shall be entitled
to obtain from any court of competent jurisdiction, an injunction restraining
Shareholder from

                                       6
<PAGE>

committing the violation, without the necessity of proving actual damage and in
addition to any other relief available under this Agreement or at law.

          6.  Piggy-Back Registration Rights.
              ------------------------------

          (a) If at any time or from time to time the Company shall determine to
register any of its equity securities, either for its own account or the account
of a security holder or holders (other than a registration of securities
relating solely to employee benefit plans or to effect a merger or other
reorganization), the Company will promptly give to Shareholder written notice
thereof and, upon the written request of Shareholder, include in such
registration (and any related qualification under blue sky laws or other
compliance), and in any underwriting involved therein, all the Shares specified
in the written request made within 10 business days after receipt of such
written notice from the Company.

          (b) If the registration of which the Company gives notice is for a
registered public offering involving an underwriting, the Company shall so
advise Shareholder as a part of the written notice given to Shareholder.  In
such event the right of any Shareholder to registration pursuant to this Section
6 shall be conditioned upon Shareholder's participation in such underwriting,
and the inclusion of Shares in the underwriting shall be limited to the extent
provided herein.  Shareholder (together with the Company and the other holders
distributing their securities through such underwriting) shall enter into an
underwriting agreement in customary form with the managing underwriter selected
for such underwriting by the Company.  Notwithstanding any other provision of
this Section 6, if the managing underwriter determines that marketing factors
require a limitation of the number of shares to be underwritten, the managing
underwriter may exclude some or all of the Shares or securities of other holders
of similar registration rights from such registration.  The Company shall so
advise Shareholder and other stockholders distributing their securities through
such underwriting, and the number of Shares or securities of other holders of
similar registration rights that may be included in the registration and
underwriting, as determined by the managing underwriter, shall be allocated on a
pro rata basis.  If Shareholder disapproves of the terms of any such
underwriting, Shareholder may elect to withdraw therefrom by written notice to
the Company and the managing underwriter.  Any securities excluded or withdrawn
from such underwriting shall be withdrawn from such registration, and shall
continue to be subject to the terms of this Section.

          (c) The Company shall have the right to terminate or withdraw any
registration initiated by it under this Section 6 prior to the effectiveness of
such registration whether or not Shareholder has elected to include securities
in such registration.

          (d) All expenses associated with the registration (including, without
limitation, registration, qualification and filing fees, printing expenses, blue
sky fees, and fees and disbursements of counsel and accountants for the Company)
shall be borne by the

                                       7
<PAGE>

Company. Selling expenses, including underwriters' discounts, shall be borne by
Shareholder pro rata in proportion to the number of securities being registered.

          (e) In the case of each registration under this Section, the Company
will:

              (i)   prepare and file a registration statement with respect to
such securities and use its best efforts to cause such registration statement to
become and remain effective for at least 45 days or until the distribution
described in the registration statement has been completed, whichever first
occurs;

              (ii)  furnish to Shareholder such reasonable number of copies of
the registration statement, preliminary prospectus, final prospectus and such
other documents as Shareholder may reasonably request in order to facilitate the
public offering of the Shares; and

              (iii) use its best efforts to register and qualify the securities
covered by such registration statement under such other securities or blue sky
laws of such jurisdictions as shall be reasonably requested by Shareholder,
provided that the Company shall not be required in connection therewith or as a
condition thereto to qualify as a foreign corporation or as a dealer in
securities or to file a general consent to service of process in any such states
or jurisdictions in which it has not already done so and except as may be
required by the Securities Act.

          (f) The Company will indemnify Shareholder against all expenses,
claims, losses, damages or liabilities (or actions in respect thereof), arising
out of or based on any untrue statement (or alleged untrue statement) of a
material fact contained in any registration statement, prospectus, offering
circular or other document, or any amendment or supplement thereto, incident to
any such registration, or based on any omission (or alleged omission) to state
therein a material fact required to be stated therein or necessary to make the
statements therein, in light of the circumstances in which they were made, not
misleading, or any violation by the Company of the Securities Act of 1933, the
Securities Exchange Act of 1934, state securities law or any rule or regulation
promulgated under such laws applicable to the Company in connection with any
such registration, qualification or compliance, and the Company will reimburse
Shareholder for any legal and any other expenses reasonably incurred, as such
expenses are incurred, in connection with investigating, preparing or defending
any such claim, loss, damage, liability or action, provided that the Company
will not be liable in any such case to the extent that any such claim, loss,
damage, liability or expense arises out of or is based on any untrue statement
or omission, or alleged untrue statement or omission, made in reliance upon and
in conformity with written information furnished to the Company by an instrument
duly executed by Shareholder.

          (g) Shareholder will, if Shares held by such Shareholder are included
in the securities as to which such registration is being effected, indemnify the
Company, each of its directors and officers, each underwriter, if any, of the
Company's securities covered by such a

                                       8
<PAGE>

registration statement against all claims, losses, damages and liabilities (or
actions in respect thereof) arising out of or based on any untrue statement (or
alleged untrue statement) of a material fact contained in any such registration
statement, prospectus, offering circular or other document, or any omission (or
alleged omission) to state therein a material fact required to be stated therein
or necessary to make the statements therein not misleading, and will reimburse
the Company, such Shareholders, such directors, officers, persons, underwriters
or control persons for any legal or any other expenses reasonably incurred, as
such expenses are incurred, in connection with investigating or defending any
such claim, loss, damage, liability or action, in each case to the extent, but
only to the extent, that such untrue statement (or alleged untrue statement) or
omission (or alleged omission) is made in such registration statement,
prospectus, offering circular or other document in reliance upon and in
conformity with written information furnished to the Company by an instrument
duly executed by Shareholder and stated to be specifically for use therein.

          (h) Shareholder shall furnish to the Company such information
regarding Shareholder, the Shares held by Shareholder, and the distribution
proposed by Shareholder as the Company may request in writing and as shall be
required in connection with any registration referred to in this Agreement.

          (i) The registration rights granted to Shareholder in this Section
shall expire at such time (if ever) as Shareholder is free to sell the Shares
under Rule 144 promulgated under the Securities Act (or any successor thereto)
without limitation as to volume or manner of sale restrictions.

          7.  Co-Sale Rights.
              --------------

          (a) In the event that Founder receives a bona fide offer from any
person to purchase any of Founder's Common Stock (the "Founder's Shares") in a
private transaction exempt from registration under the Securities Act, Founder
shall give Shareholder notice of his intention to sell Founder's Shares,
describing the amount of Founder's Shares proposed to be transferred, the
identity of the proposed transferee, and the price and terms upon which he
proposes to make such transfer (the "Transfer Notice").

          (b) Within fifteen (15) days after delivery of the Transfer Notice,
Shareholder may elect to sell up to Shareholder's pro rata share of the total
number of shares to be purchased by the transferee described in the Transfer
Notice by giving written notice thereof to Founder and tendering to Founder a
certificate representing the shares to be sold, properly endorsed for transfer,
with written instructions to transfer the shares to the transferee described in
the Transfer Notice upon receipt of payment for such shares from such transferee
for the benefit of Shareholder.  Founder shall thereupon notify the transferee
of the co-sale arrangements hereunder, and instruct the transferee to deliver
payment for the shares to be purchased from Shareholder to Shareholder.  For the
purpose of the co-sale right set forth in this Section, the pro rata share of
Shareholder shall be determined based on the number of

                                       9
<PAGE>

Shares held by Shareholder that are subject to co-sale rights, divided by the
sum of (A) the total number of shares of common stock held by all stockholders
of the Company (including Shareholder) holding similar co-sale rights plus (B)
the number of shares of common stock held by Founder at the date of the Transfer
Notice (assuming conversion of all convertible securities and exercise of all
options and warrants). The resulting percentage shall then be multiplied by the
number of Shares proposed to be purchased by the transferee to determine the
actual number of Shares eligible for sale by Shareholder.

          (c)  In the event Shareholder declines to exercise the co-sale right
as allowed by this Section, Founder may, within 90 days after the date on which
Shareholder's co-sale rights lapsed, transfer some or all of Founder's Shares
which were the subject of the Transfer Notice at a price and on terms no less
favorable to the transferee(s) than specified in the Transfer Notice. Founder's
Shares transferred in accordance with the provisions of this Section shall no
longer be subject to the restrictions on Founder's Shares forth in this Section.
After the expiration of said 90-day period, Founder shall not transfer any of
Founder's Shares without again complying with this Section.

          (d)  Any transfer of Founder's Shares without consideration to a
family member of Founder or a trust or custodian for the benefit of Founder or a
family member of Founder, and transfers pursuant to a pledge to secure
indebtedness, shall not be subject to the provisions of this Section, provided
that the transferee agrees in writing to be bound by the provisions of this
Section with respect to any subsequent transfer of such shares.

          8.   Legend. Each certificate for Shares owned by Shareholder shall
               ------
bear the following legends:

          (a)  The shares represented by this certificate were issued to
          the shareholder with restrictions.  Neither the shares, nor any
          interest in them, may be sold, transferred, assigned, pledged,
          hypothecated, or otherwise disposed of, if restricted pursuant
          to a stock rights agreement between the shareholder and the
          Company, a copy of which is on file at the office of the
          Company in Fairport, New York.

          (b)  The shares represented by this certificate have not been
          registered under the Securities Act of 1933, as amended, and
          may not be transferred in the absence of such registration unless
          the Company receives an opinion of counsel reasonably acceptable
          to it stating the such sale or transfer is exempt from registration.

With respect to Shares that are subject to the Purchase Option described in
Section 3 of this Agreement, however, Shareholder shall be entitled to a
certificate without the legend set forth

                                       10
<PAGE>

in subparagraph (a), evidencing any Shares as to which the Company's Purchase
Option has expired.

          9.   Notices.  All notices and communications under this Agreement
               -------
shall be in writing and shall be given by personal delivery or by registered or
certified mail, return receipt requested, addressed to the respective residences
of Shareholder and Founder set forth below or to such other address as may be
designated by Shareholder or Founder, and to the principal office of the
Company.  Notice shall be deemed given upon personal delivery or upon receipt.

          10.  Miscellaneous.
               -------------

               (a) Neither this Agreement, nor any action taken under it, shall
be construed as creating any limitation or restriction upon any right that
Subsidiary would otherwise have to terminate the employment of Shareholder at
any time for any reason.

               (b) This Agreement may be modified or amended only upon the
written consent of all parties to the Agreement.

               (c) This Agreement shall be interpreted, construed, and enforced
in accordance with the laws of the State of New York.

               (d) Neither this Agreement, nor any rights or obligations under
it, may be assigned by any party without the prior written consent of the other
parties.

               (e) This Agreement shall benefit and be binding upon the parties
and their successors, heirs, executors, personal representatives, and assigns.

               (f) This Agreement sets forth the entire understanding and
agreement of the parties with respect to its subject matter and supersedes all
prior letters, agreements, covenants, communications, understandings,
representations, or warranties, whether oral or written, by any officer,
employee, or representative of either party.

               (g) The waiver of any provision of this Agreement, or of any
breach of this Agreement, shall not constitute a subsequent waiver of any
provision or breach.

               (h) In the event that Shareholder is a prevailing party in any
litigation arising under or in connection with this Agreement, the Company shall
pay the reasonable attorneys fees and expenses incurred by Shareholder in
connection with the litigation.

               (i) If, at any time, any of the provisions of this Agreement
shall be deemed by a court or other body having jurisdiction over this Agreement
to be illegal, invalid, or unenforceable, those provisions shall be deemed
severed from this Agreement. The remaining

                                       11
<PAGE>

provisions of this Agreement shall be valid and binding as if this Agreement had
never contained any illegal, invalid, or otherwise unenforceable provisions,
without the requirement that the amendment be recorded in a writing signed by
the parties.

          The parties' assent to the terms of this Agreement is confirmed by
their signatures below.

                                        PAETEC CORP.

                                        By: /s/ Arunas A. Chesonis
                                           --------------------------------
                                                Title: President

                                        PAETEC COMMUNICATIONS, INC.

                                        By: /s/ Arunas A. Chesonis
                                           --------------------------------
                                                Title: President

Address:                                /s/ John Baron
                                        -----------------------------------
                                            John Baron
116 Selborne Chase
Fairport, New York  14450

Address:                                /s/ Arunas A. Chesonis
                                        -----------------------------------
                                            Arunas A. Chesonis
18 Buckthorn Run
Victor, New York  14564

                                       12

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