<PAGE>   1

                                                                    EXHIBIT 10.5

THE PERFORMANCE OF THIS SUBSIDIARY GUARANTY AND THE PAYMENT OF ANY AMOUNTS DUE
HEREUNDER SHALL BE SUBORDINATED TO THE EXTENT AND IN THE MANNER PROVIDED IN THAT
CERTAIN PEQUOT SUBORDINATION AGREEMENT BETWEEN THE LENDER AND FOOTHILL CAPITAL
CORPORATION, A CALIFORNIA CORPORATION (THE "SUBORDINATION AGREEMENT"). THE
LENDER AND ANY SUBSEQUENT HOLDER OF THE NOTE (AS DEFINED BELOW), BY ACCEPTANCE
THEREOF, ACKNOWLEDGE AND AGREE TO BE BOUND BY THE SUBORDINATION AGREEMENT.


                               SUBSIDIARY GUARANTY

                THIS SUBSIDIARY GUARANTY, dated as of April 20, 2001, made
jointly and severally by each of the subsidiary guarantors identified under the
caption "SUBSIDIARY GUARANTORS" on the signature pages hereto (individually, a
"Subsidiary Guarantor," and collectively, the "Subsidiary Guarantors"), in favor
of PEQUOT PRIVATE EQUITY FUND II, L.P. (the "Lender").

                              W I T N E S S E T H:

                WHEREAS, each Subsidiary Guarantor is a direct or indirect
wholly-owned subsidiary of FUTURELINK CORP., a Delaware corporation (the
"Borrower").

                WHEREAS, the Borrower has entered into a Secured Subordinated
Convertible Promissory Note, dated as of the date hereof (as such note may be
amended, modified or supplemented from time to time, the "Note") in favor of the
Lender.

                WHEREAS, the Note contemplates the execution, delivery and the
implementation of this Guaranty.

                WHEREAS, it is a condition precedent to the obligations of the
Lender under the Note that this Guaranty shall have been entered into by the
parties hereto and shall have become unconditionally and fully effective in
accordance with the terms hereof.

                WHEREAS, each Subsidiary Guarantor has duly authorized the
execution, delivery and performance of this Guaranty and will receive direct and
indirect benefits by reason of the availability of the loan extended pursuant to
the Note (the "Loan").

                NOW, THEREFORE, in order to induce the Lender to make the Loan
to the Borrower pursuant to the Note, and for other good and valuable
consideration receipt of which is hereby acknowledged by each Subsidiary
Guarantor, each Subsidiary Guarantor hereby agrees with the Lender as follows:



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                                    ARTICLE I

                                   DEFINITIONS

                SECTION 1.1 Certain Terms. The following terms (whether or not
underscored) when used in this Guaranty, including its preamble and recitals,
shall have the following meanings (such definitions to be equally applicable to
the singular and plural forms thereof):

                (a) "Borrower" has the meaning assigned to that term in the
        first recital hereto.

                (b) "Funding Subsidiary Guarantor" has the meaning assigned to
        such term in Section 4.4 hereof.

                (c) "Guaranteed Obligations" has the meaning assigned to that
        term in Section 2.1 hereof.

                (d) "Guaranty" means this Subsidiary Guaranty, as the same may
        be amended, supplemented, amended and restated or otherwise modified
        from time to time.

                (e) "Lender" has the meaning assigned to that term in the
        preamble hereto.

                (f) "Loan Documents" means the Note, the Security Agreement and
        the Guaranty.

                (g) "Note" has the meaning assigned to that term in the second
        recital hereto.

                (h) "Subsidiary Guarantor" and "Subsidiary Guarantors" have the
        respective meanings assigned to those terms in the preamble hereto.

                SECTION 1.2 Note Definitions. Unless otherwise defined herein,
terms used in this Guaranty, including its preamble and recitals, have the
meanings provided in the Note.

                                   ARTICLE II

                                    GUARANTY

                SECTION 2.1 Guaranty. Each Subsidiary Guarantor jointly and
severally with each other Subsidiary Guarantor hereby unconditionally and
irrevocably guarantees the full and prompt payment when due, whether at stated
maturity, by acceleration or otherwise (including, without limitation, all
amounts which would have become due but for the operation of the automatic stay
under Section 362(a) of the Federal Bankruptcy Code, 11 U.S.C. 362(a)), of the
following (collectively, the "Guaranteed Obligations"):

                (a) all obligations of the Borrower to the Lender now or
        hereafter existing under the Note and the Security Agreement, whether
        for principal, interest, fees, expenses or otherwise; and



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                (b) any and all expenses (including reasonable counsel fees and
        expenses) incurred by the Lender in enforcing any of their respective
        rights under this Guaranty.

                SECTION 2.2 Limitation of Subsidiary Guarantor's Liability. Each
Subsidiary Guarantor confirms that it is its intention that the guaranty by such
Subsidiary Guarantor pursuant to this Guaranty not constitute a fraudulent
transfer of conveyance for purposes of any federal, state or foreign law. To
effectuate the foregoing intention, the Subsidiary Guarantor hereby irrevocably
agrees that the obligations of each Subsidiary Guarantor under this Guaranty
shall be limited to the maximum amount as will, after giving effect to all other
contingent and fixed liabilities of such Subsidiary Guarantor and after giving
effect to any collections from payments made by or on behalf of any other
Subsidiary Guarantor in respect of the obligations of such other Subsidiary
Guarantor under this Guaranty, result in the obligations of such Subsidiary
Guarantor under this Guaranty not constituting a fraudulent conveyance or
fraudulent transfer under federal, state or foreign law.

                SECTION 2.3 Guaranty Absolute. This Guaranty shall be construed
as a continuing, absolute and unconditional guarantee of payment. Each
Subsidiary Guarantor guarantees that the Guaranteed Obligations will be paid
strictly in accordance with the terms of the Note and the other Loan Documents,
regardless of any law, regulation or order now or hereafter in effect in any
jurisdiction affecting any of such terms or the rights of, the Lender with
respect thereto. The liability of each Subsidiary Guarantor under this Guaranty
shall be absolute and unconditional irrespective of:

                (a) any lack of validity or enforceability of this Guaranty, the
        Note Agreement, any other Loan Document or any other agreement or
        instrument relating to any thereof, the absence of any action to enforce
        the same, any release of the Borrower or any other Subsidiary Guarantor,
        the recovery of any judgment against the Borrower or any Subsidiary
        Guarantor, any action to enforce the same or any other circumstance
        which might otherwise constitute a legal or equitable discharge or
        defense of a Subsidiary Guarantor;

                (b) any occurrence or condition whatsoever, including without
        limitation, (i) any compromise, settlement, release, waiver, renewal,
        extension, indulgence or modification of, or any change in, any of the
        obligations of the Borrower or any Subsidiary Guarantor contained in
        this Guaranty, the Note or any other Loan Document, (ii) any impairment,
        modification, release or limitation of the liability of the Borrower or
        any Subsidiary Guarantor or any of their estates in bankruptcy, or any
        remedy for the enforcement thereof, resulting from the operation of any
        present or future provision of any applicable bankruptcy law, as
        amended, or other statute or from the decision of any court, (iii) the
        assertion or exercise by any Subsidiary Guarantor or the Lender of any
        rights or remedies, (iv) the assignment or the purported assignment of
        any property as security for the Guaranteed Obligations, including all
        or any part of the rights of any Subsidiary Guarantor under this
        Guaranty, (v) the extension of the time for payment by the Borrower or
        any Subsidiary Guarantor of any payments or other sums or any part
        thereof owing or payable under any of the terms and provisions of any
        Loan Document or of the time for performance by the Borrower or any
        Subsidiary Guarantor of any other obligations under or arising out of
        any terms or provisions or the extension of the renewal



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        of any thereof, (vi) the modification or amendment (whether material or
        otherwise) of any duty, agreement or obligation of the Borrower or any
        Subsidiary Guarantor set forth in any Loan Document, (vii) the voluntary
        or involuntary liquidation, dissolution, sale or other disposition of
        all or substantially all of the assets, marshalling of assets and
        liabilities, receivership, insolvency, bankruptcy, assignment for the
        benefit of creditors, reorganization, arrangement, composition or
        readjustment of, or other similar proceeding affecting the Borrower or
        any of the Subsidiary Guarantors or any of their respective assets, or
        the disaffirmancy of this Guaranty or any Loan Document in any such
        proceeding, (viii) the release or discharge of the Borrower or any
        Subsidiary Guarantor from the performance or observance of any
        agreement, covenant, term or condition contained in any of such
        instruments by operation of law, (ix) the unenforceability of this
        Guaranty or any Loan Document or (x) any other circumstance which might
        otherwise constitute a legal or equitable discharge of a surety or
        guarantor; or

                (c) any exchange, release or non-perfection of any collateral,
        or any release or amendment or waiver of or consent to departure from
        any other guarantee, for all or any of the Guaranteed Obligations.

Each Subsidiary Guarantor hereby (i) waives diligence, presentment, demand of
payment, filing of claims with a court in the event of the merger, insolvency or
bankruptcy of any Subsidiary Guarantor, and all demands whatsoever, (ii)
acknowledges that any agreement, instrument or document evidencing this Guaranty
may be transferred to any affiliate of the Lender, and that the benefit of its
obligations hereunder shall extend to each holder of any agreement, instrument
or document evidencing this Guaranty without notice to them; provided, however,
that any transfer to a person or entity that is not an affiliate of the Lender
may not be made without the prior written consent of such Subsidiary Guarantor
(which consent will not be unreasonably withheld), and (iii) covenants that this
Guaranty will not be discharged except by complete performance of this Guaranty.
Each Subsidiary Guarantor further agrees that if at any time all or any part of
any payment theretofore applied by any person to this Guaranty is, or must be,
rescinded or returned for any reasons whatsoever, including without limitation,
the insolvency, bankruptcy or reorganization of the Borrower or any Subsidiary
Guarantor, this Guaranty shall, to the extent that such payment is or must be
rescinded or returned, be deemed to have continued in existence notwithstanding
such application, and this Guaranty shall continue to be effective or be
reinstated, as the case may be, as though such application had not been made.

                SECTION 2.4 Waiver. Each Subsidiary Guarantor hereby waives
promptness, diligence, notice of acceptance and any other notice with respect to
any of the Guaranteed Obligations and this Guaranty and any requirement that the
Lender protect, secure, perfect or insure any security interest or lien or any
property subject thereto or exhaust any right or take any action against the
Borrower or any other person or entity (including any other guarantor) or any
collateral.

                SECTION 2.5 Subrogation. No Subsidiary Guarantor will exercise
any rights which it may acquire by way of subrogation under this Guaranty, by
any payments made hereunder or otherwise, until all the Guaranteed Obligations
shall have been paid in full. If any amount shall be paid to any of the
Subsidiary Guarantors on account of such subrogation rights at any time when all
the Guaranteed Obligations shall not have been paid in full (whether



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pursuant to a claim in any bankruptcy or similar proceeding or otherwise), such
amount shall be held in trust for the benefit of the Lender and shall forthwith
be paid to the Lender to be credited and applied upon the Guaranteed
Obligations, whether matured or unmatured, in accordance with the terms of the
Note or any other Loan Documents.

                SECTION 2.6 Consent to Jurisdiction; Waiver of Immunities.

                (a) Each Subsidiary Guarantor hereby irrevocably submits to the
        non-exclusive in personam jurisdiction of any New York State or Federal
        court of competent jurisdiction sitting in New York City in any action
        or proceeding arising out of or relating to this Guaranty, and each
        Subsidiary Guarantor hereby irrevocably agrees that all claims in
        respect of such action or proceeding may be heard or determined in such
        New York State or Federal court. Each Subsidiary Guarantor hereby
        irrevocably waives, to the fullest extent it may effectively do so, the
        defense of an inconvenient forum to the maintenance of such action or
        proceeding. Each Subsidiary Guarantor irrevocably consents to the
        service of any and all process in any such action or proceeding by the
        mailing (by certified mail) of copies of such process to the Subsidiary
        Guarantors at their addresses specified in Section 4.2. Each Subsidiary
        Guarantor agrees that a final judgment in any such action or proceeding
        shall be conclusive and may be enforced in accordance with applicable
        law in other jurisdictions by suit on the judgment or in any other
        manner provided by law.

                (b) Nothing in this Section shall affect the right of the Lender
        to serve legal process in any other manner permitted by law or affect
        the right of the Lender to bring any action or proceeding against each
        Subsidiary Guarantor or its property in the courts of any other
        jurisdictions.

                (c) To the extent that any of the Subsidiary Guarantors has or
        hereafter may acquire any immunity from jurisdiction of any court or
        from any legal process (whether through service or notice, attachment
        prior to judgment, attachment in aid of execution, execution or
        otherwise) with respect to itself or to its property, each Subsidiary
        Guarantor hereby irrevocably waives such immunity in respect of its
        obligations under this Guaranty.

                (d) By executing this Guaranty, each Subsidiary Guarantor hereby
        irrevocably and unconditionally waives any objection which it may now or
        hereafter have to the laying of venue of any of the aforesaid actions or
        proceedings arising out of or in connection with this Guaranty brought
        in any of the aforesaid courts, and hereby further irrevocably and
        unconditionally waives and agrees not to plead any claim that any such
        action or proceeding brought in any such court has been brought in an
        inconvenient forum.



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                                   ARTICLE III

                          REPRESENTATIONS AND COVENANTS

                SECTION 3.1 Representations and Warranties. Each Subsidiary
Guarantor hereby represents and warrants to the Lender as follows:

                (a) As to representations and warranties contained in Section 2
        of the Note and in any other Loan Documents insofar as the
        representations and warranties contained therein by their terms are
        applicable to such Subsidiary Guarantor and its properties, each such
        representation and warranty (insofar as applicable as aforesaid),
        together with all related definitions and ancillary provisions, being
        hereby incorporated into this Guaranty by reference as though
        specifically set forth in this Section.

                (b) Such Subsidiary Guarantor is a corporation duly organized,
        validly existing and in good standing under the laws of the jurisdiction
        of its incorporation, and has full corporate power and authority to
        enter into this Guaranty and each other Loan Documents to which it is a
        party and to carry out the transactions contemplated hereby and thereby.

                SECTION 3.2 Covenants. Each Subsidiary Guarantor agrees with the
Lender that, until all Guaranteed Obligations shall have been paid in full, such
Subsidiary Guarantor will perform, comply with and be bound by all of the
agreements, covenants and obligations contained in the Loan Documents which by
their terms are applicable to such Subsidiary Guarantor or its properties, each
such agreement, covenant and obligation contained in such Loan Documents,
together with all related definitions and ancillary provisions, being hereby
incorporated into this Guaranty by reference as though specifically set forth in
this Section shall survive only to the same extent as the obligations under the
Note and Security Agreement survive.


                                   ARTICLE IV

                                  MISCELLANEOUS

                SECTION 4.1 Amendments, Etc. No amendment or waiver of any
provision of this Guaranty nor consent to any departure by any of the Subsidiary
Guarantors therefrom shall in any event be effective unless the same shall be in
writing and signed by the Lender and each Subsidiary Guarantor, and then such
waiver or consent shall be effective only in the specific instance and for the
specific purpose for which given.

                SECTION 4.2 Addresses for Notices. All notices, requests,
consents and demands shall be made in writing and shall be mailed postage
prepaid, or delivered by reliable overnight courier service, or delivered by
hand, to the Borrower or to the Holder at their respective addresses set forth
below or to such other address as may be furnished in writing to the other party
hereto and shall be effective upon receipt:



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                If to a Subsidiary Guarantor, to FutureLink Corp., at 2 South
Pointe Drive, Lake Forest, California 92630, Attention: Chief Financial Officer
and General Counsel.

                If to the Lender, at Pequot Capital Management, Inc., 500 Nyala
Farm Road, Westport, Connecticut 06880, Attention: Carol Holley and Amber
Tencic.

                SECTION 4.3 No Waiver; Remedies. No failure on the part of the
Lender to exercise, and no delay in exercising, any right hereunder shall
operate as a waiver thereof; nor shall any single or partial exercise of any
right hereunder preclude any other or further exercise thereof or the exercise
of any other right. The remedies herein provided are cumulative and not
exclusive of any remedies provided by law or equity.

                SECTION 4.4 Contribution Obligations among Subsidiary
Guarantors. In order to provide for just and equitable contribution among the
Subsidiary Guarantors, the Subsidiary Guarantors agree, among themselves, that
in the event any payment or distribution is made by a Subsidiary Guarantor (a
"Funding Subsidiary Guarantor") under this Guaranty, such Funding Subsidiary
Guarantor shall be entitled to a contribution from the other Subsidiary
Guarantors for all such payments or distributions, or damages and expenses
incurred by such Funding Subsidiary Guarantor in discharging any Guaranteed
Obligations. Each Subsidiary Guarantor which is not a Funding Subsidiary
Guarantor shall be liable to a Funding Subsidiary Guarantor with respect to any
such payments or distributions, or damages and expenses, in an aggregate amount
equal to (a) the ratio of (i) the net worth of such Subsidiary Guarantor, as
determined in accordance with the most recent balance sheet of such Subsidiary
Guarantor at the time of such payment by a Funding Subsidiary Guarantor, to (ii)
the aggregate net worth of all Subsidiary Guarantors, similarly determined,
multiplied by (b) the amount which the Funding Subsidiary Guarantor paid on
account of the Guaranteed Obligations. In the event that at any time there
exists more than one Funding Subsidiary Guarantor, then payment from the other
Subsidiary Guarantors pursuant to this Section shall be in an aggregate amount
equal in proportion to the total amount of money paid for or on account of the
Guaranteed Obligations by the Funding Subsidiary Guarantors pursuant to this
Guaranty. If the Funding Subsidiary Guarantor is required to make any payment
hereunder, such Funding Subsidiary Guarantor shall also be entitled to a right
of subrogation in respect of such payment from the other Subsidiary Guarantors.
Notwithstanding anything in this Section to the contrary, the agreements in this
Section are to establish the relative rights of contribution of the Subsidiary
Guarantors and shall not modify the joint and several nature of the obligations
of each Subsidiary Guarantor owed to the Lender or impair the rights of the
Lender to hold any of the Subsidiary Guarantors liable for payment of the full
amount of all Guaranteed Obligations.

                SECTION 4.5 Continuing Guaranty. This Guaranty is a continuing
guaranty and shall (a) remain in full force and effect until final payment in
full of the Guaranteed Obligations and all other amounts payable under this
Guaranty, subject to reinstatement in accordance with Section 2.2 hereof, (b) be
jointly and severally binding upon each of the Subsidiary Guarantors, their
successors and assigns, and (c) inure to the benefit of and be enforceable by
the Lender and their respective successors, permitted transferees and assigns;
provided, however, that no Subsidiary Guarantor may assign or transfer any of
its obligations hereunder without the prior written consent of the Lender.



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                SECTION 4.6 Subordination. Notwithstanding anything to the
contrary in this Guaranty, all rights of the Lender under by this Guaranty,
shall be subordinate to the rights of the holders of the Senior Indebtedness.

                SECTION 4.7 Severability. Any provision of this Guaranty which
is prohibited or unenforceable in any jurisdiction shall, as to such
jurisdiction, be ineffective to the extent of such prohibition or
unenforceability without invalidating the remaining provisions of this Guaranty
or affecting the validity or enforceability of such provisions in any other
jurisdiction.

                SECTION 4.8 Governing Law. This Guaranty shall be governed by,
and construed in accordance with, the internal laws of the State of New York.



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                IN WITNESS WHEREOF, each of the parties hereto has caused this
Guaranty to be duly executed and delivered by its officer thereunto duly
authorized as of the date first above written.


                                            SUBSIDIARY GUARANTORS


                                            FUTURELINK PLEASANTON CORP., a
                                            Delaware corporation


                                            By: /s/ HOWARD E. TAYLOR
                                               ---------------------------------
                                               Howard E. Taylor, President
                                               and Chief Executive Officer


                                            FUTURELINK MICRO VISIONS CORP., a
                                            Delaware corporation


                                            By: /s/ HOWARD E. TAYLOR
                                               ---------------------------------
                                               Howard E. Taylor, President
                                               and Chief Executive Officer


                                            FUTURELINK VSI CORP., a Maryland
                                            corporation


                                            By: /s/ HOWARD E. TAYLOR
                                               ---------------------------------
                                               Howard E. Taylor, President
                                               and Chief Executive Officer


                                            FUTURELINK MADISON CORP., a Delaware
                                            corporation


                                            By: /s/ HOWARD E. TAYLOR
                                               ---------------------------------
                                               Howard E. Taylor, President
                                               and Chief Executive Officer



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                                            FUTURELINK ASYNC CORP., a Delaware
                                            corporation


                                            By: /s/ HOWARD E. TAYLOR
                                               ---------------------------------
                                               Howard E. Taylor, President
                                               and Chief Executive Officer


                                            3045207 NOVA SCOTIA COMPANY, a Nova
                                            Scotia corporation


                                            By: /s/ HOWARD E. TAYLOR
                                               ---------------------------------
                                               Howard E. Taylor, President
                                               and Chief Executive Officer


                                            1423280 ONTARIO INC., an Ontario
                                            corporation


                                            By: /s/ HOWARD E. TAYLOR
                                               ---------------------------------
                                               Howard E. Taylor, President
                                               and Chief Executive Officer


                                            FUTURELINK CANADA CORP., an Ontario
                                            corporation

                                            By: /s/ HOWARD E. TAYLOR
                                               ---------------------------------
                                               Howard E. Taylor, President
                                               and Chief Executive Officer



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                                            LENDER


                                            PEQUOT PRIVATE EQUITY FUND II, L.P.,
                                            a Delaware limited partnership


                                            By: Pequot Capital Management, Inc.,
                                                its Investment Manager


                                            By: /s/ KEVIN E. O'BRIEN
                                               ---------------------------------
                                               Kevin E. O'Brien, General Counsel



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