<PAGE>   1
                                                                  EXHIBIT 10.1.4

                 FOURTH AMENDMENT TO LOAN AND SECURITY AGREEMENT

     THIS FOURTH AMENDMENT TO LOAN AND SECURITY AGREEMENT (this "Amendment") is
made and entered into as of this 8th day of May, 2001, by and among THE CIT
GROUP/BUSINESS CREDIT, INC., a New York corporation (hereinafter "CITBC"), in
its individual capacity and as Agent for the Lenders hereinafter named
(hereinafter the "AGENT"), Foothill Capital Corporation, a California
corporation ("FCC"), The CIT Group/Equipment Financing, Inc., a Delaware
corporation ("CITEF"), and any other party hereafter becoming a Lender pursuant
to Section 13, Paragraph 9 of the Agreement (as hereinafter defined), each
individually sometimes referred to as a "LENDER" and, collectively, the
"LENDERS"), and UTI Drilling, L.P., a Texas limited partnership ("UTI"), Norton
Drilling, L.P., a Delaware limited partnership, as successor in interest (by
conversion) to Norton Drilling Company, a Delaware corporation ("NDLP"),
Universal Well Services, Inc., a Delaware corporation ("UWSI"), UTI Management
Services, L.P., a Texas limited partnership ("UTIMS"), and Suits Drilling
Company, an Oklahoma corporation ("SDC"), (UTI, NDLP, UWSI, UTIMS and SDC,
together with any additional entities which may become a Company under the
Agreement from time to time, being referred to herein individually as a
"COMPANY" and, collectively, as the "COMPANIES").

                                    RECITALS

     A. WHEREAS, pursuant to the terms and subject to the conditions of that
certain Loan and Security Agreement dated as of November 22, 1999 between the
parties hereto (such Loan and Security Agreement, as the same is hereby amended
and may hereafter be amended from time to time, being hereinafter referred to as
the "Agreement"), the Companies were granted a $90,000,000 revolving line of
credit which included a letter of credit facility;

     B. WHEREAS, the indebtedness of the Companies to the Lenders is currently
evidenced by that certain Revolving Loan Promissory Note dated October 18, 2000
(the "Existing Revolving Note"), executed by the Companies and payable to CITBC
as Agent for the benefit of the Lenders in the stated principal amount of
$90,000,000.00;

     C. WHEREAS, payment of the Obligations of the Companies is currently
supported by the guaranties of UTI Energy Corp., a Delaware corporation ("UTI
ENERGY"), UTICO, Inc., a Delaware corporation ("HOLDING"), UTICO Hard Rock
Boring, Inc., a Delaware corporation ("UHRB"), International Petroleum Services
Company, a Pennsylvania corporation ("IPSCO"), Norton Drilling Services, Inc., a
Delaware corporation ("NDS"), Norton Drilling Company Mexico, Inc., a Delaware
corporation ("NDM") and UTI Drilling Canada, Inc., a Delaware corporation ("UTI
CANADA") (UTI Energy, Holding, UHRB, IPSCO, NDS, NDM and UTI Canada are referred
to herein, individually, as a "GUARANTOR" and, collectively, as the
"GUARANTORS");

     D. WHEREAS, to secure, in part, the indebtedness under the Agreement and
the Existing Revolving Note (and all renewals, extensions, modifications and/or
rearrangements thereof and in connection therewith) and all other indebtedness,
liabilities and obligations of the Companies to the Agent for the benefit of the
Lenders, then existing or thereafter arising, the Companies have heretofore

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 1
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executed in favor of the Agent certain Loan Documents (as defined in the
Agreement), including, without limitation, the Guaranty (as defined in the
Agreement), which Loan Documents shall continue as amended in connection
herewith in full force and effect upon the execution of this Amendment and shall
continue to secure the payment by the Companies of the Obligations (as defined
in the Agreement) all as more fully set forth therein and herein;

     E. WHEREAS, (i) the Companies have requested and, pursuant to the terms and
subject to the conditions hereof and in connection herewith, the Agent and the
Lenders have agreed to remove UTI Energy as a Guarantor, and (ii) the parties
have agreed to decrease the amount of the Line of Credit (as defined in the
Agreement) to $70,000,000 and the Companies accept the Revolving Note (as herein
defined) in replacement and substitution (but not extinguishment) of the
Existing Revolving Note;

     F. WHEREAS, in furtherance of the foregoing and to evidence the agreements
of the parties hereto in relation thereto the parties hereto desire to amend the
Agreement as hereinafter provided;

     NOW, THEREFORE, in consideration of the premises herein contained and other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Companies, the Agent and the Lenders, intending to be legally
bound, agree as follows:

                                    AGREEMENT

                                    ARTICLE I
                                   DEFINITIONS

     1.01 Capitalized terms used in this Amendment are defined in the Agreement,
as amended hereby, unless otherwise stated herein.

                                   ARTICLE II
                             AMENDMENTS TO AGREEMENT

     Effective as of the respective date herein indicated, the Agreement is
hereby amended as follows:

     2.01 DEFINITION OF "GUARANTOR" AND "GUARANTORS". Effective as of the date
of this Amendment, the references to "Guarantor" and "Guarantors" in the
preamble to the Agreement and in the definition of "Guarantor" set forth in
Section 1 of the Agreement are amended to delete UTI Energy. Effective as of the
date of this Amendment, neither UTI Energy nor the Parent shall constitute (i) a
"Guarantor" or an "Obligor" under the Agreement, or (ii) a party to, or have any
obligation or liability under, the Agreement.

     2.02 AMENDMENT AND RESTATEMENT OF DEFINITION OF "ACQUISITION FACILITY
COMMITMENT". Effective as of the date of this Amendment, the definition of
"Acquisition Facility Commitment" set forth in Section 1 of the Agreement is
amended and restated to read in its entirety as follows:

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 2
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               "'ACQUISITION FACILITY COMMITMENT' shall mean, with respect to
          any Lender, a portion of the Revolving Loans which may be advanced as
          Acquisition Facility Loans, evidencing the amount of its commitment to
          make Acquisition Facility Loans (all such loans being Revolving
          Loans), as modified from time to time pursuant to the terms hereof,
          not to exceed $50,000,000 in the aggregate."

     2.03 AMENDMENT AND RESTATEMENT OF DEFINITION OF "APPLICABLE MARGIN".
Effective as of the date of this Amendment, the definition of "Applicable
Margin" set forth in Section 1 of the Agreement is amended and restated to read
in its entirety as follows:

               "APPLICABLE MARGIN" means, with respect to any amount outstanding
          made under any LIBOR Loans or Revolving Loans other than LIBOR Loans,
          as the case may be, the rate of interest per annum determined as set
          forth below:

               (a) during the period from the Closing Date through the Financial
          Statement Delivery Date (as defined below) for the fiscal quarter
          ending on December 31, 1999:

<Table>
<Caption>
                AS TO REVOLVING LOANS                            AS TO
               OTHER THAN LIBOR LOANS                         LIBOR LOANS
               ----------------------                         -----------

<S>                                                           <C>
                       0.25%                                     2.25%
</Table>

               (b) during the period between any two Financial Statement
          Delivery Dates for any Margin Period occurring after December 31,
          1999, the rate determined by reference to the pricing grid below as a
          function of the amount of TTM EBITDA:

<Table>
<Caption>
                                                                      AS TO REVOLVING LOANS                  AS TO
                       TTM EBITDA                                     OTHER THAN LIBOR LOANS              LIBOR LOANS
                       ----------                                     ----------------------              -----------
<S>                                                                   <C>                                 <C>
        > or = to $55,000,000                                                 0.00%                         1.75%
        < $55,000,000 and > or = to $45,000,000                               0.00%                         2.00%
        < $45,000,000 and > or = to $35,000,000                               0.25%                         2.25%
        < $35,000,000 and > or = to $30,000,000                               0.50%                         2.50%
        < $30,000,000                                                         0.75%                         2.75%
</Table>

          As used herein, "FINANCIAL STATEMENT DELIVERY DATE" means the earlier
     of (i) the last day on which the quarterly or annual financial statements
     of the Companies are to be delivered to the Agent and the Lenders pursuant
     to Section 7, Paragraph 8(a), or (ii) the date upon which such financial
     statements actually are delivered to the Agent and the Lenders. As used
     herein, "MARGIN PERIOD" means a period commencing on the most recent
     Financial Statement Delivery Date and ending on the next Financial
     Statement Delivery Date. Each change in the Applicable Margin shall become
     effective on the first

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 3
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     day of the calendar month next following the applicable Financial Statement
     Delivery Date."

The parties confirm and agree that from the date of this Amendment through and
including the Financial Statement Delivery Date for the fiscal quarter ending
June 30, 2001, the Applicable Margin (a) for Revolving Loans other than LIBOR
Loans shall be 0.00% and (b) for LIBOR Loans shall be 1.75%.

     2.04 AMENDMENT AND RESTATEMENT OF DEFINITION OF "EARLY TERMINATION FEE".
Effective as of the date of this Amendment, the definition of "Early Termination
Fee" set forth in Section 1 of the Agreement is amended and restated to read in
its entirety as follows:

               " `EARLY TERMINATION FEE' shall: (a) mean the fee the Agent on
          behalf of the Lenders is entitled to charge the Companies if the
          Companies terminate the Line of Credit or this Agreement on a date
          prior to the fourth anniversary of the Closing Date; and (b) be
          determined by multiplying the Line of Credit by (i) one half of one
          percent (0.50%) if the Early Termination Date occurs on or prior to
          one year (1) after the Merger Date, (ii) three-tenths of one percent
          (0.30%) if the Early Termination Date occurs more than one (1) year
          after the Merger Date but on or prior to three (3) years after the
          Closing Date; and (iii) two-tenths of one percent (0.20%) if the Early
          Termination Date occurs more than three (3) years after the Closing
          Date but prior to four (4) years after the Closing Date."

     2.05 AMENDMENT AND RESTATEMENT OF DEFINITION OF "EBITDA". Effective as of
the date of this Amendment, the definition of "EBITDA" set forth in Section 1 of
the Agreement is amended and restated to read in its entirety as follows:

               " `EBITDA' shall mean, in any period, all earnings before all (a)
          interest and tax obligations, (b) depreciation and depletion and (c)
          amortization for said period, all determined in accordance with GAAP
          on a basis consistent with the latest audited financial statements of
          the Companies, the Parent and their respective consolidated
          Subsidiaries but excluding for any such period (i) the effect of
          extraordinary and non-reoccurring gains or losses and non-cash
          compensation expense (ii) restructure charges arising in connection
          with the Merger, (iii) other charges related to (A) the Merger or (B)
          changes to indebtedness for borrowed money arising in connection with
          the Merger, (iv) write downs and write offs of deferred finance
          charges as a result of the reduction in total committed credit
          facilities, and (v) charges related to financing costs associated with
          the Patterson Loan Agreement or this Agreement (but excluding accruals
          for interest expense); provided, however, the aggregate amount of the
          items in clauses (ii) through (v) above shall not exceed $20,000,000."

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 4
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     2.06 AMENDMENT AND RESTATEMENT OF DEFINITION OF "LINE OF CREDIT". Effective
as of the date of this Amendment, the definition of "Line of Credit" set forth
in Section 1 of the Agreement is amended and restated to read in its entirety as
follows:

               " `LINE OF CREDIT' shall mean the commitment of the Lenders in
          the aggregate amount of $70,000,000 to (a) make Revolving Loans
          pursuant to Sections 3 and 4 of this Agreement, and (b) assist the
          Companies in opening Letters of Credit pursuant to Section 5 of this
          Agreement (up to the Letter of Credit Sub-Line)."

     2.07 NEW DEFINITIONS. Effective as of the date of this Amendment, Section 1
of the Agreement is amended by adding the following new definitions thereto, to
be inserted in appropriate alphabetical order:

               "LOANS" shall mean shall mean the loans and advances made, from
          time to time, to or for the account of each Company by the Agent on
          behalf of the Lenders pursuant to Section 3 or Section 4 of this
          Agreement.

               "MERGER" shall mean the merger between Patterson Energy, Inc., a
          Delaware corporation, and UTI Energy Corp., a Delaware corporation.

               "MERGER DATE" shall mean May 8, 2001 which is the effective date
          of the Merger.

               "PARENT" shall mean Patterson Energy, Inc., a Delaware
          corporation, successor in interest by merger to UTI Energy Corp., a
          Delaware corporation.

               "PATTERSON LOAN AGREEMENT" shall mean that certain Loan and
          Security Agreement dated December 21, 1999, as subsequently amended,
          between Patterson Drilling Company and Transamerica Equipment
          Financial Services Corporation.

               "PATTERSON NEGATIVE PLEDGE ASSETS" shall mean all assets of
          Parent and the Patterson Subsidiaries which would constitute
          Collateral (as such term is originally defined in the Patterson Loan
          Agreement without any amendments thereto) if the Parent and the
          Patterson Subsidiaries were a "Borrower" under the Patterson Loan
          Agreement.

               "PATTERSON SUBSIDIARIES" shall mean all of the Subsidiaries of
          the Parent immediately prior to the Merger and any corporation or
          other entity which becomes a Subsidiary of Parent after the Merger
          Date (other than as a result of the Merger).

     2.08 AMENDMENT AND RESTATEMENT OF SECTION 4, PARAGRAPH 1 OF THE AGREEMENT.
Effective as of the date of this Amendment, Section 4, Subparagraph 1(a)(i) of
the Agreement is amended and restated to read in its entirety as follows:

          "(a) (i) Following the making of such Revolving Loan and consummation
          of the Permitted Acquisition, there is at least $15 million of
          Availability (determined without

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 5
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          regard to the Excluded L/Cs) and no more than an aggregate of $50
          million of Revolving Loans outstanding, and (ii) until the Obligors
          have invested in the aggregate $25 million in cash (whether cash on
          hand or cash provided from Revolving Loans to consummate Permitted
          Acquisitions pursuant to this Section 4) in Permitted Acquisitions
          that are Domestic Acquisitions, the aggregate amount of Revolving
          Loans outstanding for the purpose of consummating Canadian
          Acquisitions cannot exceed the sum of (A) $20 million plus (B) the
          amount of cash invested in Domestic Acquisitions (whether cash on hand
          or cash provided from Revolving Loans); or"

     2.09 AMENDMENT OF SECTION 7, PARAGRAPH 10D. Effective as of the date of
execution of this Amendment, Section 7, Paragraph 10D of the Agreement is
amended by adding the following clauses (ix) and (x):

               "(ix) the lease of any or all of the Rigs and other Equipment of
               any Obligor to the Parent or the Patterson Subsidiaries, so long
               as (a) such Obligor is Solvent after giving effect to such lease,
               (b) such Obligor has received reasonably equivalent value in
               consideration of the lease, (c) such lease does not transfer
               ownership of the leased assets to the lessee, (d) such lease is
               an Operating Lease and the term thereof is no longer than one
               hundred fifty (150) days, (e) such lease by its terms is
               subordinate (in form and substance reasonably satisfactory to the
               Agent) to the liens and security interests created hereunder in
               favor of Agent and the other Lenders, (f) only one (1) original
               of such lease is executed and such original lease is delivered to
               Agent promptly after its execution to hold as Collateral under
               this Agreement, (g) the lessee under such lease executes a
               certificate for the benefit of Agent and the other Lenders (in
               form and substance reasonably satisfactory to Agent) agreeing and
               confirming that ownership of the leased assets remains with the
               lessor, and (h) the Agent for the benefit of the Lenders retains
               a fully perfected, first-priority lien in the assets leased; and

               (x) the sale of Inventory, Rig Accessories and unbilled Accounts
               of any Obligor to Parent or the Patterson Subsidiaries, so long
               as (a) such Obligor is Solvent after giving effect to such sale,
               (b) such Obligor has received the Fair Market Value of such
               assets in consideration for such sale, (c) any Rig Accessories to
               be sold are not attached to, and their sale would not adversely
               effect the value of, any Eligible Equipment, (d) the proceeds for
               such sales are promptly remitted to Agent to be applied against
               the Obligations, and (e) the aggregate proceeds for such sales
               does not exceed $60,000,000."

     2.10 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 10, SUBPARAGRAPH E
OF THE AGREEMENT. Effective as of the date of this Amendment, Section 7,
Paragraph 10, Subparagraph E, clause (i) of the Agreement is amended and
restated to read in its entirety as follows:

               "(i) the merger or consolidation of any Subsidiary of UTI Energy
               Corp. in existence on the date of this Agreement into any one or
               more of the Companies in a transaction in which a Company is the
               surviving Person and no Person other than a Company receives any
               consideration or if such consideration is

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 6
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               paid to others that are not Subsidiaries, if such payment would
               be permitted to be made if it was made as a Restricted Payment
               (and in such case such payment shall constitute a Restricted
               Payment for all purposes of this Agreement);"

     2.11 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 10, SUBPARAGRAPH I
OF THE AGREEMENT. Effective as of the date of this Amendment, Section 7,
Paragraph 10, Subparagraph I, clause (v) of the Agreement is amended and
restated to read in its entirety as follows:

               "(v) licenses and other transfers of patents, trademarks, trade
          names, copyrights, trade secrets, know-how and other intellectual
          property between and among any two or more of the Obligors and
          Subsidiaries of the Parent (other than the Patterson Subsidiaries);
          and"

     2.12 AMENDMENT AND RESTATEMENT OF SECTION 7, PARAGRAPH 11 OF THE AGREEMENT.
Effective as of the date of this Amendment, Section 7, Paragraph 11 of the
Agreement is amended and restated to read in its entirety as follows:

     "11. Until termination of this Agreement and payment and satisfaction in
     full of all Obligations hereunder, if any Event of Default shall occur and
     be continuing which has not been waived in writing by the Agent or if the
     Availability (determined as if the Excluded L/Cs were not outstanding)
     shall at any time be less than $15,000,000, then the Obligors agree that
     the Parent will, on a consolidated basis:

               (a) maintain as of the last day of each calendar month a Tangible
          Net Worth of not less than $375,000,000; and

               (b) maintain as of the last day of each month TTM EBITDA of not
          less than $25,000,000."

     2.13 NEW SECTION 7, PARAGRAPHS 19, 20 AND 21 OF THE AGREEMENT. Effective as
of the date of this Amendment, Section 7 of the Agreement is hereby amended by
adding thereto Paragraphs 19 and 20 to read in their entirety as follows:

               "19. The Companies agree to cause Parent to deliver to Agent all
          financial statements, reports and other documents required to be
          delivered by Parent under the terms and provisions of this Agreement.

               20. The Companies agree to deliver to Agent the following within
          sixty (60) days after the termination of financing under the Patterson
          Loan Agreement a guarantee executed and delivered by the Parent in
          favor of the Agent and the other Lenders, in form and substance
          acceptable to Agent, guaranteeing all present and future Obligations.

               21. The Companies agree hereafter to cause Parent and the
          Patterson Subsidiaries to grant no liens or security interests in any
          of the Patterson Negative

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 7
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          Pledge Assets to any Person other than Agent and the other Lenders,
          except (i) the security interests in such assets of Patterson Drilling
          Company originally granted under the Patterson Loan Agreement, and
          (ii) such liens and security interests which would constitute
          Permitted Liens if Parent and the Patterson Subsidiaries were
          "Companies" under this Agreement. The Companies represent and warrant
          that as of May 8, 2001, the Patterson Loan Agreement has not been
          amended to modify the definition of Collateral, as originally defined
          therein."

     2.14 AMENDMENT OF SCHEDULE 7(1). Effective as of the date of execution of
this Amendment, Schedule 7(1) of the Agreement is amended to change the chief
executive office for UTI, NDLP, UWSI, UTIMS, SDC, UHRB, IPSCO and NDM to 4510
Lamesa Highway, Snyder, Texas 79549.

     2.15 REVOLVING LOAN COMMITMENT. Effective as of the date of this Amendment,
the Revolving Loan Commitment for each Lender will be the amount set forth under
each Lender's name of the signature page hereof.

     2.16 AMENDMENT AND RESTATEMENT OF EXHIBIT A TO THE AGREEMENT. Effective as
of the date of this Amendment, Exhibit A to the Agreement is amended and
restated in its entirety as set forth on Exhibit A attached hereto.

                                   ARTICLE III
                              RELEASE OF UTI ENERGY

     3.01 RELEASE OF GUARANTEE OBLIGATION. Effective as of the date of this
Amendment, Agent and the Lenders hereby release UTI Energy from all liabilities
and obligations under that certain Guaranty Agreement dated November 22, 1999
executed by UTI Energy and the other Guarantors for the benefit of Agent and the
other Lenders (the "Guaranty Agreement"); provided, however, the liabilities and
obligations of the other Guarantors under the Guaranty Agreement remain
effective and have not been released.

     3.02 RELEASE OF SECURITY INTEREST. Effective as of the date of this
Amendment, Agent and the Lenders hereby (a) release their security interest in
the Collateral owned by UTI Energy, including, without limitation, the Pledged
Collateral, as such term is defined in that certain Pledge Agreement dated
November 22, 1999 executed by UTI Energy and the other Obligors for the benefit
of Agent and the other Lenders, and (b) release UTI Energy from all obligations
under the Loan Documents.

     3.03 REPRESENTATIONS AND WARRANTIES. The Companies hereby represent and
warrant to Agent and the other Lenders that all Eligible Accounts Receivable and
Eligible Equipment are owned by the Companies.

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 8
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                                   ARTICLE IV
                              CONDITIONS PRECEDENT

     4.01 CONDITIONS TO EFFECTIVENESS. The effectiveness of this Amendment is
subject to the satisfaction of the following conditions precedent in a manner
satisfactory to Agent, unless specifically waived in writing by Agent:

         (a) Agent shall have received each of the following, each in form and
substance satisfactory to Agent, in its sole discretion, and, where applicable,
each duly executed by each party thereto, other than Agent:

               (i) This Amendment, duly executed by the Companies and the
          Consent, Ratification and Release is executed by the Guarantors;

               (ii) a Certificate Regarding Merger executed by Patterson Energy,
          Inc. confirming the merger between Patterson Energy, Inc. and UTI
          Energy Corp. has closed and is effective;

               (iii) articles of merger and all other documents necessary under
          applicable state law are filed with the Secretary of State of Delaware
          to effectuate the merger between Patterson Energy, Inc., a Delaware
          corporation, and UTI Energy Corp., a Delaware corporation;

               (iv) A Revolving Loan Promissory Note (the "Revolving Note") in
          the stated principal amount of $70,000,000 in amendment, substitution
          and replacement (but not extinguishment) of the Existing Revolving
          Note duly signed by the Companies;

               (v) certified copies of the resolutions of the Board of Directors
          of each of the Companies and the Guarantors authorizing the execution,
          delivery and performance of the Revolving Note, this Amendment and any
          and all other Loan Documents executed by any of the Companies or the
          Guarantors in connection therewith, along with a certificate of
          incumbency certified by the secretary of each of the Companies and the
          Guarantors with specimen signatures of the officers of the Companies
          and the Guarantors who are authorized to sign such documents, all in
          form and substance satisfactory to the Agent; and

               (vi) All other documents Agent may request with respect to any
          matter relevant to this Amendment or the transactions contemplated
          hereby.

         (b) The representations and warranties contained herein and in the
Agreement and the other documents executed in connection with the Agreement
(herein referred to as "Loan Documents"), as each is amended hereby, shall be
true and correct as of the date hereof, as if made on the date hereof.

         (c) No Default or Event of Default shall have occurred and be
continuing, unless such Default or Event of Default has been otherwise
specifically waived in writing by Agent.

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 9
<PAGE>   10

         (d) All corporate proceedings taken in connection with the transactions
contemplated by this Amendment and all documents, instruments and other legal
matters incident thereto shall be satisfactory to Agent.

                                   ARTICLE V
                 RATIFICATIONS, REPRESENTATIONS AND WARRANTIES

     5.01 RATIFICATIONS. The terms and provisions set forth in this Amendment
shall modify and supersede all inconsistent terms and provisions set forth in
the Agreement and the other Loan Documents, and, except as expressly modified
and superseded by this Amendment, the terms and provisions of the Agreement and
the other Loan Documents are ratified and confirmed and shall continue in full
force and effect. The Companies, Agent and the Lenders agree that the Agreement
and the other Loan Documents, as amended hereby, shall continue to be legal,
valid, binding and enforceable in accordance with their respective terms.

     5.02 REPRESENTATIONS AND WARRANTIES. The Companies hereby represent and
warrant to Agent and the Lenders that (a) the execution, delivery and
performance of this Amendment and any and all other Loan Documents executed
and/or delivered in connection herewith have been authorized by all requisite
corporate or limited partnership action (as applicable) on the part of the
Companies and will not violate the Articles (or Certificates) of Incorporation
or Bylaws of the Companies that are corporations or the limited partnership
agreements or certificates of limited partnership of the Companies that are
limited partnerships; (b) each of the Company's Board of Directors (or the
general partner of the applicable limited partnership) has authorized the
execution, delivery and performance of this Amendment and any and all other Loan
Documents executed and/or delivered in connection herewith; (c) the
representations and warranties contained in the Agreement, as amended hereby,
and any other Loan Document are true and correct on and as of the date hereof
and on and as of the date of execution hereof as though made on and as of each
such date; (d) no Default or Event of Default under the Agreement, as amended
hereby, has occurred and is continuing, unless such Default or Event of Default
has been specifically waived in writing by Agent; (e) the Companies are in full
compliance with all covenants and agreements contained in the Agreement and the
other Loan Documents, as amended hereby; and (f) the Companies have not amended
their Articles (or Certificates) of Incorporation or their Bylaws since the date
of the Agreement, except as otherwise disclosed to Agent.

                                   ARTICLE VI
                            MISCELLANEOUS PROVISIONS

     6.01 SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations and
warranties made in the Agreement or any other Loan Document, including, without
limitation, any document furnished in connection with this Amendment, shall
survive the execution and delivery of this Amendment and the other Loan
Documents, and no investigation by Agent or any closing shall affect the
representations and warranties or the right of Agent to rely upon them.

     6.02 REFERENCE TO AGREEMENT. Each of the Agreement and the other Loan
Documents, and any and all other Loan Documents, documents or instruments now or
hereafter executed and delivered pursuant to the terms hereof or pursuant to the
terms of the Agreement, as amended hereby, are hereby

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 10
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amended so that any reference in the Agreement and such other Loan Documents to
the Agreement shall mean a reference to the Agreement, as amended hereby.

     6.03 EXPENSES OF AGENT. As provided in the Agreement, the Companies agree
to pay on demand all reasonable costs and expenses incurred by Agent in
connection with the preparation, negotiation, and execution of this Amendment
and the other Loan Documents executed pursuant hereto and any and all
amendments, modifications, and supplements thereto, including, without
limitation, the reasonable costs and fees of Agent's legal counsel, and all
reasonable costs and expenses incurred by Agent in connection with the
enforcement or preservation of any rights under the Agreement, as amended
hereby, or any other Loan Documents, including, without limitation, the
reasonable costs and fees of Agent's legal counsel.

     6.04 SEVERABILITY. Any provision of this Amendment held by a court of
competent jurisdiction to be invalid or unenforceable shall not impair or
invalidate the remainder of this Amendment and the effect thereof shall be
confined to the provision so held to be invalid or unenforceable.

     6.05 SUCCESSORS AND ASSIGNS. This Amendment is binding upon and shall inure
to the benefit of Agent and the Companies and their respective successors and
assigns, except that the Companies may not assign or transfer any of their
rights or obligations hereunder without the prior written consent of Agent.

     6.06 COUNTERPARTS. This Amendment may be executed in one or more
counterparts, each of which when so executed shall be deemed to be an original,
but all of which when taken together shall constitute one and the same
instrument.

     6.07 EFFECT OF WAIVER. No consent or waiver, express or implied, by Agent
to or for any breach of or deviation from any covenant or condition by the
Companies shall be deemed a consent to or waiver of any other breach of the same
or any other covenant, condition or duty.

     6.08 HEADINGS. The headings, captions, and arrangements used in this
Amendment are for convenience only and shall not affect the interpretation of
this Amendment.

     6.09 APPLICABLE LAW. THIS AMENDMENT AND ALL OTHER LOAN DOCUMENTS EXECUTED
PURSUANT HERETO SHALL BE DEEMED TO HAVE BEEN MADE AND TO BE PERFORMABLE IN AND
SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
NEW YORK.

     6.10 FINAL AGREEMENT. THE AGREEMENT AND THE OTHER LOAN DOCUMENTS, EACH AS
AMENDED HEREBY, REPRESENT THE ENTIRE EXPRESSION OF THE PARTIES WITH RESPECT TO
THE SUBJECT MATTER HEREOF ON THE DATE THIS AMENDMENT IS EXECUTED. THE AGREEMENT
AND THE OTHER LOAN DOCUMENTS, AS AMENDED HEREBY, MAY NOT BE CONTRADICTED BY
EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES.
THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES. NO MODIFICATION,
RESCISSION, WAIVER, RELEASE OR AMENDMENT OF ANY

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 11
<PAGE>   12

PROVISION OF THIS AMENDMENT SHALL BE MADE, EXCEPT BY A WRITTEN AGREEMENT SIGNED
BY COMPANIES AND AGENT.

     6.11 RELEASE. THE COMPANIES HEREBY ACKNOWLEDGE THAT THEY HAVE NO DEFENSE,
COUNTERCLAIM, OFFSET, CROSS-COMPLAINT, CLAIM OR DEMAND OF ANY KIND OR NATURE
WHATSOEVER THAT CAN BE ASSERTED TO REDUCE OR ELIMINATE ALL OR ANY PART OF ITS
LIABILITY TO REPAY THE "OBLIGATIONS" OR TO SEEK AFFIRMATIVE RELIEF OR DAMAGES OF
ANY KIND OR NATURE FROM AGENT. THE COMPANIES HEREBY VOLUNTARILY AND KNOWINGLY
RELEASE AND FOREVER DISCHARGE AGENT, THE LENDERS AND THEIR RESPECTIVE
PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS AND ASSIGNS, FROM ALL POSSIBLE
CLAIMS, DEMANDS, ACTIONS, CAUSES OF ACTION, DAMAGES, COSTS, EXPENSES, AND
LIABILITIES WHATSOEVER, KNOWN OR UNKNOWN, ANTICIPATED OR UNANTICIPATED,
SUSPECTED OR UNSUSPECTED, FIXED, CONTINGENT, OR CONDITIONAL, AT LAW OR IN
EQUITY, ORIGINATING IN WHOLE OR IN PART ON OR BEFORE THE DATE THIS AMENDMENT IS
EXECUTED, WHICH THE COMPANIES MAY NOW OR HEREAFTER HAVE AGAINST AGENT, THE
LENDERS AND THEIR RESPECTIVE PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS AND
ASSIGNS, IF ANY, AND IRRESPECTIVE OF WHETHER ANY SUCH CLAIMS ARISE OUT OF
CONTRACT, TORT, VIOLATION OF LAW OR REGULATIONS, OR OTHERWISE, AND ARISING FROM
ANY "LOANS", INCLUDING, WITHOUT LIMITATION, ANY CONTRACTING FOR, CHARGING,
TAKING, RESERVING, COLLECTING OR RECEIVING INTEREST IN EXCESS OF THE HIGHEST
LAWFUL RATE APPLICABLE, THE EXERCISE OF ANY RIGHTS AND REMEDIES UNDER THE
AGREEMENT OR OTHER LOAN DOCUMENTS, AND NEGOTIATION FOR AND EXECUTION OF THIS
AMENDMENT. The foregoing release does not pertain to, affect, terminate, reduce
or limit any losses, costs, claims, expenses, causes of action or damages that
the Companies or their affiliates may have (whether known or unknown) against
GMAC Business Credit, LLC ("GMAC"), and its predecessors, agents (other than
Agent), employees, successors and assigns (other than Agent and the other
Lenders), including without limiting the generality of the foregoing, such
losses, costs, claims, expenses, causes of action or damages as may arise or
exist in connection with any prior, present or future demand by GMAC for any
premium, fee or charge to be paid, directly or indirectly, by the Companies to
GMAC as a result of GMAC's withdrawal from the credit facilities contemplated in
the Agreement as amended hereby, or the payment of the outstanding amounts.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT - Page 12
<PAGE>   13

     IN WITNESS WHEREOF, this Amendment has been executed and is effective as of
the date first above-written.

                         COMPANIES:

                         UTI DRILLING, L.P.
                         UTI MANAGEMENT SERVICES, L.P.

                         By: Utico Hard Rock Boring, Inc., the sole general
                         partner of UTI Drilling, L.P. and UTI Management
                         Services, L.P.

                                 By:
                                     -------------------------------------------
                                 Name: John E. Vollmer, III
                                 Title: Vice President

                         NORTON DRILLING, L.P.

                         By: Norton GP, L.L.C., its sole general partner
                             By: Norton Drilling Services, Inc., as Sole Member
                                 of Norton GP, L.L.C.

                                 By:
                                     -------------------------------------------
                                 Name:
                                       -----------------------------------------
                                 Title:
                                        ----------------------------------------


                         UNIVERSAL WELL SERVICES, INC.
                         SUITS DRILLING COMPANY

                                 By:
                                     -------------------------------------------
                                 Name: John E. Vollmer, III
                                 Title: Vice President of each of the
                                        foregoing Companies


                         LENDERS:

                         THE CIT GROUP/BUSINESS CREDIT, INC.
                         as Agent and Lender

                         By:
                             ---------------------------------------------------
                         Name:
                               -------------------------------------------------
                         Title:
                                ------------------------------------------------

                         Revolving Loan Commitment:  $30,000,000.00

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT
<PAGE>   14

                                       FOOTHILL CAPITAL CORPORATION
                                       as Documentation Agent and Lender

                                       By:
                                           -------------------------------------
                                       Name:
                                             -----------------------------------
                                       Title:
                                              ----------------------------------

                                       Revolving Loan Commitment: $30,000,000.00


                                       THE CIT GROUP/EQUIPMENT FINANCING, INC.

                                       By:
                                           -------------------------------------
                                       Name:
                                             -----------------------------------
                                       Title:
                                              ----------------------------------

                                       Revolving Loan Commitment: $10,000,000.00

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT
<PAGE>   15

                        CONSENT, RATIFICATION AND RELEASE

     The undersigned each hereby consents to the terms of the within and
foregoing Amendment, confirms and ratifies the terms of that certain Guaranty
Agreement dated November 22, 1999 executed (or assumed) by the undersigned for
the benefit of Agent and the other Lenders (the "Guaranty Agreement"), and
acknowledges that the Guaranty Agreement is in full force and effect and
ratifies the same, that the undersigned each has no defense, counterclaim,
set-off or any other claim to diminish the undersigned's liability under such
document, that the undersigned's consent is not required to the effectiveness of
the within and foregoing Amendment, and that no consent by the undersigned is
required for the effectiveness of any future amendment, modification,
forbearance or other action with respect to the Obligations, the Collateral, or
any of the other Loan Agreements. THE UNDERSIGNED EACH HEREBY VOLUNTARILY AND
KNOWINGLY RELEASES AND FOREVER DISCHARGES AGENT, THE OTHER LENDERS AND THEIR
RESPECTIVE PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS AND ASSIGNS, FROM ALL
POSSIBLE CLAIMS, DEMANDS, ACTIONS, CAUSES OF ACTION, DAMAGES, COSTS, EXPENSES,
AND LIABILITIES WHATSOEVER, KNOWN OR UNKNOWN, ANTICIPATED OR UNANTICIPATED,
SUSPECTED OR UNSUSPECTED, FIXED, CONTINGENT, OR CONDITIONAL, AT LAW OR IN
EQUITY, ORIGINATING IN WHOLE OR IN PART ON OR BEFORE THE DATE THIS AMENDMENT IS
EXECUTED, WHICH THE UNDERSIGNED MAY NOW OR HEREAFTER HAVE AGAINST AGENT, THE
OTHER LENDERS AND THEIR RESPECTIVE PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS
AND ASSIGNS, IF ANY, AND IRRESPECTIVE OF WHETHER ANY SUCH CLAIMS ARISE OUT OF
CONTRACT, TORT, VIOLATION OF LAW OR REGULATIONS, OR OTHERWISE, AND ARISING FROM
ANY "LOANS", INCLUDING, WITHOUT LIMITATION, ANY CONTRACTING FOR, CHARGING,
TAKING, RESERVING, COLLECTING OR RECEIVING INTEREST IN EXCESS OF THE HIGHEST
LAWFUL RATE APPLICABLE, THE EXERCISE OF ANY RIGHTS AND REMEDIES UNDER THE LOAN
AGREEMENT OR OTHER AGREEMENTS, AND NEGOTIATION FOR AND EXECUTION OF THIS
AMENDMENT. The foregoing release does not pertain to, affect, terminate, reduce
or limit any losses, costs, claims, expenses, causes of action or damages that
the undersigned Guarantors or their affiliates may have (whether known or
unknown) against GMAC Business Credit, LLC ("GMAC"), and its predecessors,
agents (other than Agent), employees, successors and assigns (other than Agent
and the other Lenders), including without limiting the generality of the
foregoing, such losses, costs, claims, expenses, causes of action or damages as
may arise or exist in connection with any prior, present or future demand by
GMAC for any premium, fee or charge to be paid, directly or indirectly, by any
of the undersigned Guarantors to GMAC as a result of GMAC's withdrawal from the
credit facilities contemplated in the Agreement as amended by the foregoing
Amendment, or the payment of the outstanding amounts.

GUARANTORS:                                    UTICO, INC.

UTI DRILLING CANADA, INC.
UTICO HARD ROCK BORING, INC.                   By:
NORTON DRILLING SERVICES, INC.                     ----------------------------
NORTON DRILLING COMPANY                            Kenneth J. Kubacki
         MEXICO, INC.                              Vice President and Treasurer
INTERNATIONAL PETROLEUM
          SERVICES COMPANY


By:
     ----------------------------------------
     John E. Vollmer III, Vice President
     signing as such on behalf of each of the
     foregoing Obligors

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT
<PAGE>   16

                        CONSENT, RATIFICATION AND RELEASE

     The undersigned, UTI Energy Corp., hereby consents to the terms of the
within and foregoing Amendment. THE UNDERSIGNED HEREBY VOLUNTARILY AND KNOWINGLY
RELEASES AND FOREVER DISCHARGES AGENT, THE OTHER LENDERS AND THEIR RESPECTIVE
PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS AND ASSIGNS, FROM ALL POSSIBLE
CLAIMS, DEMANDS, ACTIONS, CAUSES OF ACTION, DAMAGES, COSTS, EXPENSES, AND
LIABILITIES WHATSOEVER, KNOWN OR UNKNOWN, ANTICIPATED OR UNANTICIPATED,
SUSPECTED OR UNSUSPECTED, FIXED, CONTINGENT, OR CONDITIONAL, AT LAW OR IN
EQUITY, ORIGINATING IN WHOLE OR IN PART ON OR BEFORE THE DATE THIS AMENDMENT IS
EXECUTED, WHICH THE UNDERSIGNED MAY NOW OR HEREAFTER HAVE AGAINST AGENT, THE
OTHER LENDERS AND THEIR RESPECTIVE PREDECESSORS, AGENTS, EMPLOYEES, SUCCESSORS
AND ASSIGNS, IF ANY, AND IRRESPECTIVE OF WHETHER ANY SUCH CLAIMS ARISE OUT OF
CONTRACT, TORT, VIOLATION OF LAW OR REGULATIONS, OR OTHERWISE, AND ARISING FROM
ANY "LOANS", INCLUDING, WITHOUT LIMITATION, ANY CONTRACTING FOR, CHARGING,
TAKING, RESERVING, COLLECTING OR RECEIVING INTEREST IN EXCESS OF THE HIGHEST
LAWFUL RATE APPLICABLE, THE EXERCISE OF ANY RIGHTS AND REMEDIES UNDER THE LOAN
AGREEMENT OR OTHER AGREEMENTS, AND NEGOTIATION FOR AND EXECUTION OF THIS
AMENDMENT. The foregoing release does not pertain to, affect, terminate, reduce
or limit any losses, costs, claims, expenses, causes of action or damages that
the undersigned or its affiliates may have (whether known or unknown) against
GMAC Business Credit, LLC ("GMAC"), and its predecessors, agents (other than
Agent), employees, successors and assigns (other than Agent and the other
Lenders), including without limiting the generality of the foregoing, such
losses, costs, claims, expenses, causes of action or damages as may arise or
exist in connection with any prior, present or future demand by GMAC for any
premium, fee or charge to be paid, directly or indirectly, by any of the
undersigned to GMAC as a result of GMAC's withdrawal from the credit facilities
contemplated in the Agreement as amended by the foregoing Amendment, or the
payment of the outstanding amounts.


UTI ENERGY CORP.


By:
    ------------------------------------
    John E. Vollmer III, Vice President

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT
<PAGE>   17

                                    EXHIBIT A
                         REVOLVING LOAN PROMISSORY NOTE

                                   May 8, 2001

$70,000,000

FOR VALUE RECEIVED, the undersigned Companies (each a "COMPANY" and,
collectively, the "COMPANIES"), promise, jointly and severally, to pay to the
order of THE CIT GROUP/BUSINESS CREDIT, INC. (herein "CITBC"), as Agent for the
Lenders under a certain Loan and Security Agreement dated November 22, 1999
between CITBC as Agent and Lender, other Lenders parties thereto and each
Company, as amended from time to time (herein the "AGREEMENT") at its office
located at 1211 Avenue of the Americas, New York, New York 10036, or such other
address as may be designated by the Agent, in lawful money of the United States
of America and in immediately available funds, the principal amount of Seventy
Million and No/100 Dollars ($70,000,000), or such other principal amount
advanced pursuant to Section 3, Paragraph 1 or Section 4 of the Agreement. The
balance of such Revolving Loan will fluctuate as a result of the daily
application of the proceeds of collections of the Accounts and the making of
additional Revolving Loans as described in said Section 3 or Section 4 of the
Agreement. The Revolving Loans may be borrowed, repaid and reborrowed by any
Company, subject to the terms of the Agreement. A final payment in an amount
equal to the outstanding aggregate balance of principal and interest remaining
unpaid, if any, under this Revolving Loan Promissory Notes as shown on the books
and records of the Agent shall be due and payable upon any termination of the
Agreement.

All capitalized terms used herein shall have the meaning provided therefor in
this Agreement, unless otherwise defined herein.

The Companies further promise, jointly and severally, to pay interest at such
office, in like money, on the unpaid principal amount owing hereunder from time
to time from the date hereof on the dates and at the rates specified in Section
8, Paragraph 1 of the Agreement.

If any payment on this Revolving Loan Promissory Note becomes due and payable on
a day other than a Business Day, the maturity thereof shall be extended to the
next succeeding Business Day, and with respect to payments of principal,
interest thereon shall be payable at the then applicable rate during such
extension.

This Revolving Loan Promissory Note is a Revolving Loan Promissory Note referred
to in the Agreement, and is subject to, and entitled to, all provisions and
benefits thereof and is subject to optional and mandatory prepayment, in whole
or in part, as provided therein.

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT
<PAGE>   18

The date and amount of the advance(s) made hereunder may be recorded on the
schedule which is attached hereto and hereby made part of this Note or the
separate ledgers maintained by the Agent, provided that any failure to record
any such information on such schedule shall not in any manner affect the
obligation of any Company to make payments of principal and interest in
accordance with the terms of this Revolving Loan Promissory Note. The aggregate
unpaid principal amount of all advances made pursuant hereto may be set forth in
the balance column on said schedule or such ledgers maintained by the Agent. All
such advances, whether or not so recorded, shall be due as part of this
Revolving Loan Promissory Note.

Each Company confirms that any amount received by or paid to the Agent in
connection with this Agreement and/or any balances standing to its credit on any
of its accounts on the Agent's books under this Agreement may in accordance with
the terms of this Agreement be applied in reduction of this Revolving Loan
Promissory Note, but no balance or amounts shall be deemed to effect payment in
whole or in part of this Revolving Loan Promissory Note unless the Agent shall
have actually charged such account or accounts for the purposes of such
reduction or payment of this Revolving Loan Promissory Note.

Upon the occurrence and during the continuance of any one or more of the Events
of Default specified in the Agreement or upon termination of this Agreement, all
amounts then remaining unpaid on this Revolving Loan Promissory Note may become,
or be declared to be, immediately due and payable as provided in the Agreement.

Each Company and the Guarantors, sureties and endorsers jointly and severally
waive grace, demand, presentment for payment, notice of dishonor or default,
notice of intent to accelerate, notice of acceleration, protest and diligence in
collecting this Revolving Loan Promissory Note.

This Revolving Loan Promissory Note shall be governed by, and construed in
accordance with, the laws of the State of New York and the applicable federal
laws of the United States.

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT
<PAGE>   19

This Revolving Loan Promissory Note is given in amendment, replacement and
substitution, but not extinguishment, of all amounts unpaid under that certain
Revolving Loan Promissory Note dated October 18, 2000 payable by the Companies
to the order of CITBC as Agent for the Lenders in the stated principal amount of
$90,000,000.00.

                     COMPANIES:

                     UTI DRILLING, L.P.

                     By: UTICO HARD ROCK BORING, INC.,
                         as sole General Partner

                         By:
                             --------------------------------------------------
                             John E. Vollmer III, Vice President

                     SUITS DRILLING COMPANY

                     By:
                         ------------------------------------------------------
                         John E. Vollmer III, Vice President

                     UNIVERSAL WELL SERVICES, INC.

                     By:
                         ------------------------------------------------------
                         John E. Vollmer III, Vice President

                     UTI MANAGEMENT SERVICES, L.P.

                     By: UTICO HARD ROCK BORING,
                         as Sole General Partner

                         By:
                             --------------------------------------------------
                             John E. Vollmer III, Vice President

                     NORTON DRILLING, L.P.

                     By: Norton GP, L.L.C., as sole General Partner

                         By: Norton Drilling Services, Inc., its sole Member

                             By:
                                 ---------------------------------------------
                             Name:
                                   -------------------------------------------
                             Title:
                                    ------------------------------------------

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT
<PAGE>   20

                                SCHEDULE TO GRID

<Table>
<Caption>
             Date                           Loan                        Payment                       Balance
<S>                                   <C>                           <C>                          <C>

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</Table>

FOURTH AMENDMENT TO LOAN & SECURITY AGREEMENT