<PAGE>

                                                                     Exhibit 4.1



                         SECOND AMENDMENT TO NOTE AND
                          LOAN AND SECURITY AGREEMENT
                          ---------------------------


     THIS AMENDMENT TO NOTE AND LOAN AND SECURITY AGREEMENT ("Second Amendment")
made this 30th day of September, 1999, by and between Allin Corporation,
successor by name change to Allin Communications Corporation, a Delaware
corporation, Allin Interactive Corporation, a Delaware corporation, Allin
Digital Imaging Corp., a Delaware corporation, Allin Corporation of California
d/b/a Allin Consulting, successor by name change to Kent Consulting Group, Inc.,
a California corporation, Allin Network Products, Inc., successor by name change
to Netright, Inc., a California corporation, Allin Holdings Corporation, a
Delaware corporation, and Allin Consulting of Pennsylvania, Inc., successor by
name change to KCS Computer Services, Inc., a Pennsylvania corporation, all with
a current mailing address of c/o Allin Corporation, 400 Greentree Commons, 381
Mansfield Avenue, Pittsburgh, Pennsylvania 15220-2751 (collectively, the
"Borrower")

                                 A
                                    N
                                       D

S & T BANK, having its office at 800 Philadelphia Street, Box 190, Indiana,
Pennsylvania 15701, (hereinafter referred to as "Bank").

                                 WITNESSETH:
<PAGE>

     WHEREAS, Borrower has executed and delivered to Bank a Revolving Credit
Note dated October 1, 1998 (the "Note") in the original principal amount of Five
Million Dollars ($5,000,000.00), (the "Loan") representing sums advanced or to
be advanced pursuant to a Loan and Security Agreement between the Borrower and
the Bank dated October 1, 1998, as such Loan and Security Agreement may be
amended, modified or supplemented from time to time (the "Loan Agreement").

     WHEREAS, such Note and Loan Agreement were modified by an Amendment to Note
and Loan and Security Agreement, dated March 25, 1999 (the "First Amendment"),
(the First Amendment and Second Amendment are collectively referred to herein as
the "Amendments").

     WHEREAS, the parties hereto desire to amend the Note, the Loan Agreement,
and all other documents executed in connection with the Loan (the "Loan
Documents") to extend the Expiration Date, as defined on the Loan Agreement, and
the establish a quarterly Cash Flow Coverage Ratio review period.

     NOW THEREFORE, in consideration of the foregoing recitals, and in further
consideration of the mutual covenants contained herein, and intending to be
legally bound hereby, the parties hereto agree as follows:

     1.  The foregoing recitals are incorporated herein and made a part hereof,
as and for the agreement of the parties.

                                 AMENDMENTS
                                 ----------

     2.  The parties hereto acknowledge and agree that the outstanding principal
balance of the Note as of the date hereof is One Million Dollars
($1,000,000.00).
<PAGE>

     3.  The definition of the term "Expiration Date" as defined in Paragraph
9.1 of the Loan Agreement shall be modified as follows:

          "Expiration Date" means September 30, 2000 unless extended in writing
          by the Bank."

All references in the Loan Agreement, the Note or any other Loan Document to the
"Expiration Date" are hereby amended and modified to mean "Expiration Date" as
herein defined.

     4.  Paragraph 6.16 of the Loan Agreement is hereby deleted in its entirety,
and in lieu thereof, the following provision is inserted:

          "6.16  Cash Flow Coverage Ratio.  The Borrower shall maintain, at all
                 ------------------------
          times during the Loan Term, a Cash Flow Coverage of no less than 1.0
          to 1.0.  "Cash Flow Coverage" for these purposes means, for each
          quarter during Borrower's fiscal year, (i) the Cash Flow, plus the
          aggregate interest expense incurred and paid by the Borrower during
          the period (determined in accordance with GAAP), divided by (ii) the
          aggregate interest expense incurred and paid by the Borrower during
          the period (determined in accordance with GAAP).

          "Cash Flow" for these purposes means the total operating revenues
          received from the operation of Borrower's business(es) prior to any
          withdrawal by principals and deductions for interest, depreciation and
          amortization, less all deductions from income such as administrative
          and general expenses.

          Beginning with the fiscal quarter commencing October 1, 1999, Cash
          Flow Coverage shall be analyzed quarterly during the Loan Term."

     5.  The execution of this Second Amendment to Note and Loan and Security
Agreement shall be deemed the execution of a Note in the amount of Five Million
Dollars ($5,000,000.00) upon the terms and provisions contained in the Note
executed by Borrower in favor of Bank, dated October 1, 1998, as modified by the
Amendments, and shall serve as additional evidence of Borrower's liability,
promise and undertaking, to repay the outstanding principal sum of up to Five
Million Dollars ($5,000,000.00) to Bank in accordance with the terms, covenants,
provisions and conditions contained in the Note, the Loan and Security
<PAGE>

Agreement and the other Loan Documents, and as modified herein, which terms,
covenants, provisions and conditions are incorporated herein by reference
thereto.

     6.  Anything contained herein to the contrary notwithstanding, this Second
Amendment to Note and Loan and Security Agreement will not forfeit the
precedence or prior in time lien or priority of the financing statements or any
other security held by the Bank, its successors and assigns, on the Collateral
as defined in the Loan Agreement.


                   COVENANTS, REPRESENTATIONS AND WARRANTIES
                   -----------------------------------------

     7.  The Borrower confirms and agrees that the terms:

          "Loan Document" and "Loan Documents" as defined in the Loan Agreement
each include within their respective meanings this Amendment and all other
documents and instruments executed or to be executed by the Borrower in
connection with the Second Amendment, which are collectively referred to herein
as the "Second Amendment Documents."

     8.  The Borrower ratifies, confirms and reaffirms, without condition, all
the terms and conditions of the Loan Agreement and the other Loan Documents and
agrees that it continues to be bound by the terms and conditions thereof as
amended by the First Amendment and this Second Amendment; and the Borrower
further confirms and affirms that it has no defense, set off or counterclaim
against the same.  The Loan Agreement and the Amendments shall be construed as
complementing each other and as augmenting and not restricting the Bank's
rights, and, except as specifically amended by the Amendments, the Loan
Agreement shall remain in full force and effect in accordance with its terms.

     9.  The Borrower ratifies, confirms and reaffirms without condition, all
liens and security interests granted to Bank pursuant to the Loan Agreement and
the Loan Documents, as defined in the Loan Agreement, and such liens and
security interest shall continue to secure the
<PAGE>

indebtedness and obligations of the Borrower to the Bank under the Loan
Agreement, the Note and the other Loan Documents.

     10.  The Borrower represents and warrants to the Bank that:

          (a) This Second Amendment and the other Second Amendment Documents
have been duly executed and delivered by the Borrower and constitute the legal,
valid and binding obligations of the Borrower enforceable in accordance with
their respective terms;

          (b) The execution and delivery of this Second Amendment by the
Borrower and the performance and observance by the Borrower of the provisions
hereof and the Second Amendment Documents, do not violate or conflict with the
organizational documents of Borrower or any law applicable to Borrower or result
in a breach of any provision of or constitute a default under any other
agreement, instrument or document binding upon or enforceable against Borrower;

          (c) The representations and warranties set forth within the Loan
Agreement continue to be true and correct in all material respects as of the
date of this Second Amendment except those changes resulting from the passage of
time; and

          (d) No material adverse change has occurred in the business,
operations, consolidated financial condition or prospects of the Borrower since
the date of the most recent annual financial statement delivered to the Bank and
no Event of Default or condition, which, with the passage of time, the giving of
notice or both, could become an Event of Default (a "Potential Default") has
occurred and is continuing.

     11.  The Borrower agrees to pay the fees and expenses of counsel of the
Bank in preparing and closing this Second Amendment and the Second Amendment
Documents.
<PAGE>

     12.  The Borrower shall execute or cause to be executed and delivered to
Bank all other documents, instruments and agreements deemed necessary or
appropriate by Bank in connection herewith.

                                 CONDITIONS PRECEDENT
                                 --------------------

     13.  This Second Amendment shall be effective on the date hereof so long as
each of the following conditions has been satisfied:

          (a) No Event of Default or Potential Default shall have occurred and
be continuing on the date of this Second Amendment.

          (b) The representations and warranties set forth within the Loan
Agreement shall continue to be true and correct in all material respects as of
the date of this Second Amendment except those changes resulting from the
passage of time only.

          (c) Except to the extent disclosed to the Bank in writing, no material
adverse change shall have occurred in the business, operations, financial
condition or prospects of the Borrower since the date of the last audited
financial statements delivered to the Bank.

          (d) Contemporaneously with the execution hereof, the Borrower shall
deliver, or cause to be delivered, to the Bank:

               (i) A certificate of the corporate secretary or assistant
secretary of the Borrower, dated the date hereof, certifying (1) that the
Articles of Incorporation and By-Laws of the Borrower have not been changed
since they were delivered to the Bank, or if there have been any such changes,
attaching copies thereof as then in effect and (2) as to true copies of all
corporate action taken by the Borrower in authorizing the execution, delivery
and performance of this Second Amendment and all other Second Amendment
Documents, and the transactions contemplated thereby; and
<PAGE>

               (ii) Such other documents, instruments and certificates required
by the Bank in connection with the transactions contemplated by this Second
Amendment.

     14.  The Bank shall continue to have a first priority lien on and security
interest in the Collateral, previously granted to Bank.

     15.  All legal details and proceedings in connection with the transactions
contemplated in this Second Amendment shall be satisfactory to counsel for the
Bank and the Bank shall have received all such originals or copies of such
documents as the Bank may request.

                                 MISCELLANEOUS
                                 -------------

     16.  This Second Amendment shall be construed in accordance with, and
governed by the laws of the Commonwealth of Pennsylvania without giving effect
to the provisions thereof regarding conflicts of law.

     17.  Except as amended hereby, all of the terms and conditions of the Loan
Agreement shall remain in full force and effect.  This Second Amendment amends
the Loan Agreement and is not a novation thereof.

     18.  This Second Amendment shall inure to the benefit of, and shall be
binding upon, the respective successors and assigns of the Borrower and the
Bank.  The Borrower may not assign any of its rights or obligations hereunder
without the prior written consent of the Bank.

     19.  This Second Amendment may be executed in any number of counterparts
and by the different parties hereto on separate counterparts each of which, when
so executed, shall be deemed an original, but all such counterparts shall
constitute but one and the same instrument.
<PAGE>

     IN WITNESS WHEREOF, intending to be legally bound hereby, the parties
hereto have set their hands and seals the day and year first above written.

ATTEST:                           BANK:

                                  S&T BANK


/s/ Frances N. Pape               By: /s/ David G. Antolik
    -------------------------             ----------------------------
                                          David Antolik, Vice President




ATTEST:                           BORROWER:

                                  ALLIN CORPORATION, successor by name
                                  change to ALLIN COMMUNICATIONS
                                  CORPORATION


/s/ Dean C. Praskach              By: /s/ Richard W. Talarico
    -------------------------             ----------------------------
    Secretary                     Title:




                                  ALLIN INTERACTIVE CORPORATION


/s/ Dean C. Praskach              By: /s/ Richard W. Talarico
    -------------------------             -----------------------------
    Secretary                     Title:




                                  ALLIN DIGITAL IMAGING CORP.


/s/ Dean C. Praskach              By: /s/ Richard W. Talarico
    -------------------------             -----------------------------
    Secretary                     Title:




                                  ALLIN CORPORATION OF CALIFORNIA d/b/a
                                  ALLIN CONSULTING, successor by name change
                                  to KENT CONSULTING GROUP, INC.


/s/ Dean C. Praskach              By: /s/ Richard W. Talarico
    -------------------------             -----------------------------
    Secretary                     Title:
<PAGE>

                                  ALLIN NETWORK PRODUCTS, INC., successor
                                  by name change to NETRIGHT, INC.


/s/ Dean C. Praskach              By: /s/ Richard W. Talarico
    -------------------------             -------------------------------
    Secretary                     Title:


                                  ALLIN HOLDINGS CORPORATION


/s/ Dean C. Praskach              By: /s/ Richard W. Talarico
    -------------------------             --------------------------------
    Secretary                     Title:


                                  ALLIN CONSULTING OF PENNSYLVANIA,
                                  INC., successor by name change to KCS
                                  COMPUTER SERVICES, INC.


/s/ Dean C. Praskach              By: /s/ Richard W. Talarico
    ------------------------              --------------------------------
    Secretary                     Title: