<PAGE>

                                  EXHIBIT 10.50

                                 PROMISSORY NOTE
                                 (Floating Rate)

$775,000.00                                                         May 30, 2003

     For value received, U.S. HOME SYSTEMS, INC., as principal ("Borrower"),
promises to pay to the order of THE FROST NATIONAL BANK, a national banking
association ("Lender") at P.O. Box 1600, San Antonio, Texas 78296, or at such
other address as Lender shall from time to time specify in writing, the
principal sum of SEVEN HUNDRED SEVENTY-FIVE THOUSAND AND 00/100 DOLLARS
($775,000), in legal and lawful money of the United States of America, with
interest on the outstanding principal from the date advanced until paid at the
rate set out below. Interest shall be computed on a per annum basis of a year of
360 days and for the actual number of days elapsed, unless such calculation
would result in a rate greater than the highest rate permitted by applicable
law, in which case interest shall be computed on a per annum basis of a year of
365 days or 366 days in a leap year, as the case may be.

     1. Payment Terms. Principal shall be due and payable in monthly payments of
$16,145.83 each, payable on the 30th day of each calendar month, beginning June
30, 2003, and continuing regularly thereafter until May 30, 2007, when the
entire amount hereof, principal and interest then remaining unpaid, shall be
then due and payable. Interest, computed upon the unpaid principal balance
hereof, shall be due and payable monthly as it accrues, on the same dates as,
but in addition to, said payments of principal; interest being calculated on the
unpaid principal each day principal is outstanding and all payments made
credited to any collection costs and late charges, to the discharge of the
interest accrued and to the reduction of the principal, in such order as Lender
shall determine.

     2. Late Charge. If a payment is made 10 days or more late, Borrower will be
charged, in addition to interest, a delinquency charge of (i) 5% of the unpaid
portion of the regularly scheduled payment, or (ii) $250.00, whichever is less.
Additionally, upon maturity of this Note, if the outstanding principal balance
(plus all accrued but unpaid interest) is not paid within 10 days of the
maturity date, Borrower will be charged a delinquency charge of (i) 5% of the
sum of the outstanding principal balance (plus all accrued but unpaid interest),
or (ii) $250.00, whichever is less. Borrower agrees with Lender that the charges
set forth herein are reasonable compensation to Lender for the handling of such
late payments.

     3. Interest Rate. Interest on the outstanding and unpaid principal balance
hereof shall be computed at a per annum rate equal to the lesser of (a) a rate
equal to the Wall Street Journal London Interbank Offered Rate (as defined
below) plus two and six-tenths percent (2.6%) per annum, with said rate to be
adjusted to reflect any change in The Wall Street Journal London Interbank
Offered Rate at the time of any such change or (b) the highest rate permitted by
applicable law, but in no event shall interest contracted for, charged or
received hereunder plus any other charges in connection herewith which
constitute interest exceed the maximum interest permitted by applicable law,
said rate to be effective prior to maturity (however such maturity is brought
about). The "Wall Street Journal London Interbank Offered Rate" shall mean the
London Interbank Offered Rate (LIBOR) for three (3) months quoted in the most
recently published issue of

<PAGE>

The Wall Street Journal (Central Edition) in the "Money Rates " column. If the
Wasl Street Jounral London Interbank Offered Rate ceases to be made available by
the publisher, or any successor to the publisher of The Wall Street Journal
(Central Edition), the interest rate will be determined by using a comparable
index. If more than one Wall Street Journal London Interbank Offered Rate for
three (3) months is quoted, the higher rate shall apply. The Wall Street Journal
London Interbank Offered Rate is a reference rate and does not necessarily
represent the lowest or best rate actually charged to any customer.

     4. Default Rate. Matured unpaid principal and interest shall bear interest
from date of maturity until paid at (a) the highest rate permitted by applicable
law, or (b) if no such maximum rate is established by applicable law, at the
rate stated above plus five percent (5%) per annum.

     5. Prepayment. Borrower reserves the right to prepay, prior to maturity,
all or any part of the principal of this Note without penalty. Any prepayments
shall be applied first to accrued interest and then to principal. Borrower will
provide written notice to the holder of this Note of any such prepayment of all
or any part of the principal at the time thereof. All payments and prepayments
of principal or interest on this Note shall be made in lawful money of the
United States of America in immediately available funds, at the address of
Lender indicated above, or such other place as the holder of this Note shall
designate in writing to Borrower. All partial prepayments of principal shall be
applied to the last installments payable in their inverse order of maturity.

     6. Default. It is expressly provided that upon default in the punctual
payment of this Note or any part hereof, principal or interest, within five (5)
days of the date the same shall become due and payable, or upon the occurrence
of an event of default specified in any of the other Loan Documents (as defined
below), the holder of this Note may, at its option, without further notice or
demand, (i) declare the outstanding principal balance of and accrued but unpaid
interest on this Note at once due and payable, (ii) refuse to advance any
additional amounts under this Note, (iii) foreclose all liens securing payment
hereof, (iv) pursue any and all other rights, remedies and recourses available
to the holder hereof, including but not limited to any such rights, remedies or
recourses under the Loan Documents, at law or in equity, or (v) pursue any
combination of the foregoing; and in the event default is made in the prompt
payment of this Note when due or declared due, and the same is placed in the
hands of an attorney for collection, or suit is brought on same, or the same is
collected through probate, bankruptcy or other judicial proceedings, then the
Borrower agrees and promises to pay all costs of collection, including
reasonable attorney's fees.

     7. Joint and Several Liability; Waiver. Each maker, signer, surety and
endorser hereof, as well as all heirs, successors and legal representatives of
said parties, shall be directly and primarily, jointly and severally, liable for
the payment of all indebtedness hereunder. Lender may release or modify the
obligations of any of the foregoing persons or entities, or guarantors hereof,
in connection with this loan without affecting the obligations of the others.
All such persons or entities expressly waive presentment and demand for payment,
notice of default, notice of intent to accelerate maturity, notice of
acceleration of maturity, protest, notice of protest, notice of dishonor, and
all other notices and demands for which waiver is not prohibited by law, and
diligence in the collection hereof; and agree to all renewals, extensions,
indulgences, partial payments, releases or

                                       2

<PAGE>

exchanges of collateral, or taking of additional collateral, with or without
notice, before or after maturity. No delay or omission of Lender in exercising
any right hereunder shall be a waiver of such right or any other right under
this Note.

     8. No Usury Intended; Usury Savings Clause. In no event shall interest
contracted for, charged or received hereunder, plus any other charges in
connection herewith which constitute interest, exceed the maximum interest
permitted by applicable law. The amounts of such interest or other charges
previously paid to the holder of the Note in excess of the amounts permitted by
applicable law shall be applied by the holder of the Note to reduce the
principal of the indebtedness evidenced by the Note, or, at the option of the
holder of the Note, be refunded. To the extent permitted by applicable law,
determination of the legal maximum amount of interest shall at all times be made
by amortizing, prorating, allocating and spreading in equal parts during the
period of the full stated term of the loan and indebtedness, all interest at any
time contracted for, charged or received from the Borrower hereof in connection
with the loan and indebtedness evidenced hereby, so that the actual rate of
interest on account of such indebtedness is uniform throughout the term hereof.

     9. Security. This Note has been executed and delivered pursuant to that
certain Loan Agreement of even date herewith by and between Borrower and Lender
( as from time to time amended, modified or restated, "Loan Agreement"), and is
secured by, inter alia, the following:

     (a) a Security Agreement of even date herewith, by and between Borrower and
     Lender, covering certain collateral as more particularly described therein.

     (b) Security Agreements of even date herewith, by and between each
     Guarantor (as defined in the Loan Agreement) and Lender, covering certain
     collateral as more particularly described therein.

     This Note, the Loan Agreement and all other documents evidencing, securing,
governing, guaranteeing and/or pertaining to this Note, including but not
limited to those documents described above, are hereinafter collectively
referred to as the "Loan Documents." The holder of this Note is entitled to the
benefits and security provided in the Loan Documents.

     10. Texas Finance Code. In no event shall Chapter 346 of the Texas Finance
Code (which regulates certain revolving loan accounts and revolving tri-party
accounts) apply to this Note. To the extent that Chapter 303 of the Texas
Finance Code is applicable to this Note, the "weekly ceiling" specified in such
article is the applicable ceiling; provided that, if any applicable law permits
greater interest, the law permitting the greatest interest shall apply.

     11. Governing Law, Venue. This Note is being executed and delivered, and is
intended to be performed in the State of Texas. Except to the extent that the
laws of the United States may apply to the terms hereof, the substantive laws of
the State of Texas shall govern the validity, construction, enforcement and
interpretation of this Note. In the event of a dispute involving this Note or
any other instruments executed in connection herewith, the undersigned
irrevocably agrees that venue for such dispute shall lie in any court of
competent jurisdiction in Bexar County, Texas.

                                       3

<PAGE>

     12. Purpose of Loan. Borrower agrees that no advances under this Note shall
be used for personal, family or household purposes, and that all advances
hereunder shall be used solely for business, commercial, investment, or other
similar purposes.

     13. Captions. The captions in this Note are inserted for convenience only
and are not to be used to limit the terms herein.

     14. Financial Information. Borrower agrees to promptly furnish such
financial information and statements, including financial statements in a format
acceptable to Lender, lists of assets and liabilities, agings of receivables and
payables, inventory schedules, budgets, forecasts, tax returns, and other
reports with respect to Borrower's financial condition and business operations
as Lender may request from time to time. This provision shall not alter the
obligation of Borrower to deliver to Lender any other financial statements or
reports pursuant to the terms of any other loan documents executed in connection
with this Note.

                                         BORROWER:

                                         U.S. HOME SYSTEMS, INC.


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

                                       4