<PAGE>

               U.S. SECURITIES AND EXCHANGE COMMISSION~PRIVATE ~~
                             Washington D.C. 20549


                                 FORM 10-QSB/A


(Mark One)
[X]  QUARTERLY REPORT UNDER SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT
     OF 1934


For the quarterly period ended     September 30, 1999
                                   ------------------


[  ] TRANSITION REPORT UNDER SECTION 13 OR 15(d) OF THE EXCHANGE ACT



For the transition period from_____________________ to____________


Commission file number   0-17576
                         -------

          WINDSOR PARK PROPERTIES 6, A CALIFORNIA LIMITED PARTNERSHIP
       -----------------------------------------------------------------
       (Exact name of small business issuer as specified in its charter)


         California                                  33-0299846
-----------------------------------         ---------------------------------
(State or other jurisdiction of             (IRS Employer Identification No.)
incorporation or organization)


            6160 So. Syracuse Way, Greenwood Village, Colorado 80111
            ---------------------------------------------------------
                    (Address of principal executive offices)


                                 (303) 741-3707
                       -----------------------------------
                           (Issuer's telephone number)


Check whether the issuer (1) filed all reports required to be filed by Section
13 or 15(d) of the Exchange Act during the past 12 months (or for such shorter
period that the registrant was required to file such reports), and (2) has been
subject to such filing requirements for the past 90 days.
Yes  (x)     No  (  )

Transitional small business disclosure format (check one): Yes [  ]  No [X]
<PAGE>

                               TABLE OF CONTENTS

                                     PART I
                                     ------


                                                                 Page
                                                                 ----

Item 1.    Financial Statements                                     2

Item 2.    Management's Discussion and Analysis of Financial
           Condition and Results of Operations                      8

PART II


Item 6.    Exhibits and Reports on Form 8-K                        11

           SIGNATURE                                               12
<PAGE>

                                     PART I


Certain matters discussed under "Management's Discussion and Analysis of
Financial Condition and Results of Operations" and elsewhere in this Quarterly
Report on Form 10-QSB/A may constitute forward-looking statements, and as such
involve known and unknown risks, uncertainties and other factors which may cause
the actual results, performance or achievements of Windsor Park Properties 6, A
California Limited Partnership, to be materially different from any future
results, performance or achievements expressed or implied by such
forward-looking statements.


                                       1
<PAGE>

Item 1. Financial Statements
-------

<TABLE>
<CAPTION>

                           WINDSOR PARK PROPERTIES 6
                           -------------------------
                       (A California Limited Partnership)
                                 BALANCE SHEET
                                 -------------
                                  (unaudited)

                                                                                      September 30, 1999
                                                                                 ----------------------------
 ASSETS
 ------
 Property held for investment:
<S>                                                                              <C>
  Land                                                                           $                    325,000
  Buildings and improvements                                                                        2,467,200
  Fixtures and equipment                                                                               37,000
                                                                                 ----------------------------
                                                                                                    2,829,200

 Less accumulated depreciation                                                                    (1,250,300)
                                                                                 ----------------------------
                                                                                                    1,578,900
 Investments in joint ventures and limited partnerships                                             4,672,000
 Cash and cash equivalents                                                                            347,800
 Other assets                                                                                           8,000
                                                                                 ----------------------------
 Total Assets                                                                    $                  6,606,700
                                                                                 ============================
 LIABILITIES AND PARTNERS' EQUITY
 Liabilities:
  Accrued expenses                                                               $                     93,400
  Due to General Partner and affiliates                                                                29,600
  Tenant deposits and other liabilities                                                                10,500
                                                                                 ----------------------------
 Total Liabilities                                                                                    133,500
                                                                                 ----------------------------
 Partners' equity:
  Limited partners                                                                                  6,468,500
  General partners                                                                                      4,700
                                                                                 ----------------------------
                                                                                                    6,473,200
                                                                                 ----------------------------
 Total Liabilities and Partner's Equity                                          $                  6,606,700
                                                                                 ============================
</TABLE>

                 See accompanying notes to financial statements.

                                       2
<PAGE>

<TABLE>
<CAPTION>

                           WINDSOR PARK PROPERTIES 6
                           -------------------------
                       (A California Limited Partnership)
                            STATEMENTS OF OPERATIONS
                            ------------------------
                                  (unaudited)

                                                                           Three Months Ended September 30,
                                                                      ------------------------------------------
                                                                           1999                     1998
                                                                      ---------------     ----------------------
REVENUES
--------
<S>                                                                   <C>                 <C>
Rent and utilities                                                    $       128,400     $              175,200
                                                                      ---------------     ----------------------
Equity in earnings of joint ventures and limited
 partnerships                                                                  84,600                     65,400
Interest                                                                        1,800                      4,500
Other                                                                           4,500                      5,000
                                                                      ---------------     ----------------------
                                                                             219, 300                    250,100
                                                                      ---------------     ----------------------
COSTS AND EXPENSES
------------------

Property operating                                                             54,300                     74,400
Interest                                                                            0                     31,500
Depreciation and amortization                                                  33,800                     45,200
General and administrative:
 Related parties                                                                7,700                      7,900
 Other                                                                         26,800                     14,500
                                                                      ---------------     ----------------------
                                                                              122,600                    173,500
                                                                      ---------------     ----------------------
Net income                                                            $        96,700     $               76,600
                                                                      ===============     ======================
Net income - general partners                                         $         1,000     $                  800
                                                                      ===============     ======================
Net income - limited partners                                         $        95,700     $               75,800
                                                                      ===============     ======================
Basic and diluted earnings per limited partnership
 unit                                                                 $          0.33     $                 0.26
                                                                      ===============     ======================
</TABLE>

                 See accompanying notes to financial statements.

                                       3
<PAGE>

<TABLE>
<CAPTION>

                           WINDSOR PARK PROPERTIES 6
                           -------------------------
                       (A California Limited Partnership)
                            STATEMENTS OF OPERATIONS
                            ------------------------
                                  (unaudited)

                                                                           Nine Months Ended September 30,
                                                                 -----------------------------------------------

                                                                        1999                       1998
                                                                 -------------------      ----------------------
REVENUES
--------
<S>                                                              <C>                      <C>
Rent and utilities                                               $           382,900      $              509,900
Equity in earnings of joint ventures and limited
partnerships                                                                 287,300                     197,100
Interest                                                                       5,200                      12,900
Other                                                                         13,900                      13,900
                                                                 -------------------      ----------------------
                                                                             689,300                     733,800
                                                                 -------------------      ----------------------
COSTS AND EXPENSES
------------------
Property operating                                                           161,300                     230,600
Interest                                                                           0                      95,300
Depreciation and amortization                                                100,800                     135,700
General and administrative:
 Related parties                                                              16,100                      26,300
 Other                                                                        66,800                      48,000
                                                                 -------------------      ----------------------
                                                                             345,000                     535,900
                                                                 -------------------      ----------------------
Net income                                                       $           344,300      $              197,900
                                                                 ===================      ======================
Net income - general partners                                    $             3,400      $                2,000
                                                                 ===================      ======================
Net income - limited partners                                    $           340,900      $              195,900
                                                                 ===================      ======================
Basic and diluted earnings per limited partnership unit          $              1.18      $                 0.67
                                                                 ===================      ======================
</TABLE>


                 See accompanying notes to financial statements.

                                       4
<PAGE>

<TABLE>
<CAPTION>

                           WINDSOR PARK PROPERTIES 6
                           -------------------------
                       (A California Limited Partnership)
                            STATEMENTS OF CASH FLOWS
                            ------------------------
                                  (unaudited)

                                                                               Nine Months Ended June 30,
                                                                   ----------------------------------------------
                                                                         1999                             1998
                                                                  ------------------                   ---------
Cash flows from operating activities:
<S>                                                               <C>                                 <C>
 Net income                                                       $          344,300                  $ 197,900
 Adjustments to reconcile net income to net cash
 provided by operating activities:
   Depreciation and amortization                                             100,800                    135,700
   Equity in earnings of joint ventures and limited
    partnerships                                                            (287,300)                   (197,100)
   Joint ventures' and limited partnerships cash
      distributions                                                          287,300                     197,100
   Amortization of deferred financing costs                                        0                       7,900
   Changes in operating assets and liabilities:
    Other assets                                                              (1,900)                     (8,900)
    Accounts payable                                                               0                      (2,000)
    Due to General Partners and affiliates                                    19,400                     (15,700)
    Accrued expenses                                                           8,500                      75,700
    Tenant deposits and other liabilities                                       (800)                    (23,600)
                                                                  ------------------                   ---------
Net cash provided by operating activities                                    470,300                     367,000
                                                                  ------------------                   ---------
Cash flows from investing activities:
 Joint ventures' and limited partnerships cash
   distributions                                                             310,750                     331,400
 Increase in property held for investment                                    (20,100)                    (15,100)
 Investment in joint venture and limited partnerships                        (16,350)                      2,100
                                                                  ------------------                   ---------
Net cash provided by investing activities                                    274,300                     318,400
                                                                  ------------------                   ---------
Cash flows from financing activities:
 Cash distributions                                                         (593,400)                   (591,200)
 Repurchase of limited partnership units                                     (69,300)                    (97,700)
                                                                  ------------------                   ---------
Net cash used in financing activities                                       (662,700)                   (688,900)
                                                                  ------------------                   ---------
Net decrease in cash and cash equivalents                                     81,900                      (3,500)
Cash and cash equivalents at beginning of period                             265,900                      59,300
                                                                  ------------------                   ---------
Cash and cash equivalents at end of period                        $          347,800                   $ 355,800
                                                                  ==================                   =========
</TABLE>


                 See accompanying notes to financial statements.

                                       5
<PAGE>

                           WINDSOR PARK PROPERTIES 6
                           -------------------------
                       (A California Limited Partnership)
                         NOTES TO FINANCIAL STATEMENTS
                         -----------------------------


NOTE 1.  THE PARTNERSHIP
         ---------------

Windsor Park Properties 6, A California Limited Partnership (the "Partnership"),
was formed in June 1988 for the purpose of acquiring and holding existing
manufactured home communities for investment. The General Partners of the
Partnership are The Windsor Corporation, a California corporation ("TWC"), and
John A. Coseo, Jr. In September 1998, Chateau Communities, Inc. a publicly held
real estate investment trust ("Chateau"), purchased 100% of the shares of TWC.

The Partnership was funded through a public offering of 300,000 limited
partnership units at $100 per unit which commenced in September 1988 and
terminated in June 1990. The Partnership term is set to expire in December 1999;
however, the Partnership may either be dissolved earlier or extended under
certain circumstances.


The General Partners are currently developing a plan which would liquidate and
dissolve the Partnership. The Partnership and N'Tandem Trust, an
externally-advised California business trust in which Chateau, as of September
30, 1999, held 9.8% of the outstanding capital stock ("N'Tandem"), are in
discussions with respect to a transaction whereby the Partnership would sell its
one wholly-owned property and its partial ownership interests in six other
properties to N'Tandem. The consummation of the proposed transaction with
N'Tandem would be subject to the satisfaction of certain conditions, including
the approval of a majority-in-interest of the Partnership's Limited Partners.
The General Partners expect to file with the Securities and Exchange Commission
(the "Commission") a proxy statement describing the terms of the proposed
transaction sometime in the near future and, upon clearance from the Commission,
to mail the proxy statement to Limited Partners. If the proposed transaction
with N'Tandem is consu mmated, the Partnership will be liquidated and
liquidating distributions will be made to Limited Partners in accordance with
the terms of the Partnership's Agreement of Limited Partnership. There can,
however, be no assurances that the proposed transaction with N'Tandem will be
consummated or, if consummated, that the proposed transaction will close prior
to the end of the Partnership's stated term.

NOTE 2.  BASIS OF PRESENTATION
         ---------------------

The balance sheet at September 30, 1999 and the related statements of operations
for the three and nine months ended September 30, 1999 and 1998 and the
statements of cash flows for the nine months ended September 30, 1999 and 1998
are unaudited. However, in the opinion of the General Partners, they contain all
adjustments, of a normal recurring nature, necessary for a fair presentation of
such financial statements. Interim results are not necessarily indicative of
results for a full year.


The financial statements and notes are presented as permitted by Form 10-QSB and
do not contain certain information included in the Partnership's annual
financial statements and notes on Form 10-KSB/A for the year ended December 31,
1998.

                                       6
<PAGE>

NOTE 3.  INVESTMENTS IN JOINT VENTURES AND LIMITED PARTNERSHIPS
         ------------------------------------------------------

The Partnership's investments in joint ventures and limited partnerships consist
of interests in five manufactured home communities. The combined condensed
results of operations of these properties for the nine months ended September
30, 1999 and 1998 are as follows:


<TABLE>
<CAPTION>
                                                  1999                       1998
                                     -------------------------   ------------------------
<S>                                    <C>                         <C>

   Total revenues                      $             4,445,100     $            4,224,500
   Expenses:
    Property operating                               2,031,600                  1,966,600
    Depreciation                                     1,039,300                  1,108,700
    Interest                                           682,000                    652,700
    General and administrative                          11,800                     12,000
                                     -------------------------   ------------------------
                                                     3,764,700                  3,740,000
                                     -------------------------   ------------------------
   Net income                          $               680,400     $              484,500
                                     =========================   ========================
</TABLE>


NOTE 4.  BASIC AND DILUTED EARNINGS PER LIMITED PARTNERSHIP UNIT
         -------------------------------------------------------

Basic and diluted earnings per limited partnership unit is calculated based on
the weighted average number of limited partnership units outstanding during the
period and the net income allocated to the Limited Partners.  The weighted
average number of limited partnership units outstanding during the three and
nine months ended September 30, 1999 was 287,167 and 288,135 respectively; and
291,319 and 291,576 for the three and nine months ended September 30, 1998,
respectively.

NOTE 5.  DISTRIBUTIONS TO LIMITED PARTNERS
         ---------------------------------

Distributions to Limited Partners in excess of net income allocated to Limited
Partners are considered a return of capital.  A breakdown of cash distributions
to Limited Partners for the nine months ended September 30, 1999 and 1998 is as
follows:

<TABLE>
<CAPTION>
                                                       1999                                               1998
                                 --------------------------------------------       -------------------------------------------
                                                                        Per                                               Per
                                        Amount                          Unit              Amount                          Unit
                                        ------                          ----              ------                          ----
<S>                                <C>                          <C>                   <C>                         <C>
Net income
 - Limited Partners                 $           340,900             $    1.18          $           195,800            $    0.67
Return of capital                               246,500                   .86                      404,200                 1.39
                                 ----------------------       ---------------       ----------------------      ---------------
                                    $           587,400             $    2.04          $           600,000            $    2.06
                                 ======================       ===============       ======================      ===============
</TABLE>

                                       7
<PAGE>

Item 2.
-------

               MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
               -------------------------------------------------
                      CONDITION AND RESULTS OF OPERATIONS
                      -----------------------------------

Three months ended September 30, 1999 as compared to three months ended
-----------------------------------------------------------------------
September 30, 1998
------------------

The following discussion should be read in conjunction with the financial
statements and Notes thereto included elsewhere in this Form 10-QSB/A.

Results of Operations
---------------------

The results of operations for the three months ended September 30, 1999 and 1998
are not directly comparable due to the sale of Circle K in November 1998. The
Partnership realized net income of $96,700 and $76,600 for the three months
ended September 30, 1999 and 1998, respectively. Net income per limited
partnership unit was $0.33 in 1999 and $0.26 in 1998.

Rent and utilities revenues decreased from $175,200 in 1998 to $128,400 in 1999,
due mainly to the sale of Circle K in November 1998.

Equity in earnings of joint ventures and limited partnerships represents the
Partnership's share of the net income of five manufactured home communities.
Equity in earnings of joint ventures and limited partnerships increased from
$65,400 in 1998 to $84,600 in 1999 due to rental rate increases at the five
communities.

Interest income decreased from $4,500 in 1998 to $1,800 in 1999 due mainly to
lower cash balances maintained by the Partnership.

Property operating expenses decreased from $74,400 in 1998 to $54,300 in 1999
due mainly to the sale of Circle K in November 1998.

Interest expense decreased from $31,500 in 1998 to $0 in 1999 due to the sale of
Circle K and subsequent repayment of the mortgage note payable.

General and administrative expenses increased from $22,400 in 1998 to $34,500 in
1999 primarily due to an increase in legal expenses.

Nine months ended September 30, 1999 as compared to nine months ended September
-------------------------------------------------------------------------------
30, 1998
--------

Results of Operations
---------------------

The results of operations for the nine months ended September 30, 1999 and 1998
are not directly comparable due to the sale of Circle K in November 1998. The
Partnership realized net income of $344,300 and $197,900 for the nine months
ended September 30, 1999 and 1998, respectively. Net income per limited
partnership unit was $1.18 in 1999 and $0.67 in 1998.

Rent and utilities revenues decreased from $509,900 in 1998 to $382,900 in 1999,
due mainly to the sale of Circle K in November 1998.

Equity in earnings of joint ventures and limited partnerships represents the
Partnership's share of the net income of five manufactured home communities.
Equity in earnings of joint ventures and limited partnerships increased from
$197,100 in 1998 to $287,300 in 1999 due to rental rate increases at the five
communities.

                                       8
<PAGE>

Interest income decreased from $12,900 in 1998 to $5,200 in 1999 due mainly to
lower cash balances maintained by the Partnership.

Property operating expenses decreased from $230,600 in 1998 to $161,300 in 1999
due mainly to the sale of Circle K in November 1998.

Interest expense decreased from $95,300 in 1998 to $0 in 1999 due to the sale of
Circle K and subsequent repayment of the mortgage note payable.

General and administrative expenses increased from $74,300 in 1998 to $82,900 in
1999 primarily due to an increase in legal expenses.

Liquidity and Capital Resources
-------------------------------


The Partnership's primary sources of liquidity during the nine months ended
September 30, 1999 were its cash flow generated from the operation of its
communities and distributions from investments in joint ventures and limited
partnerships. Net cash provided by operating activities was $470,300 for the
nine months ended September 30, 1999. At September 30, 1999, the Partnership's
cash amounted to $347,800.

The Partnership's primary use of cash during the same period was for cash
distributions to partners. Cash distributions to partners totaled $593,400 for
the nine months ended September 30, 1999.

The Partnership's principal long-term liquidity requirement will be the
repayment of principal on its proportionate share of outstanding joint venture
mortgage debt. At September 30, 1999, the Partnership's proportionate share of
joint venture and limited partnership debt was $6,318,400, consisting entirely
of variable rate debt. The average rate of interest on the variable rate debt
was 8.6% at September 30, 1999.

The future sources of liquidity for the Partnership will be from property
operations, cash reserves, and ultimately from the sale of communities and
investments in joint ventures and limited partnerships. The Partnership expects
to meet its short-term liquidity requirements, including capital expenditures,
administration expenses, and distributions to partners, from cash flow provided
from property operations and distributions from investments in joint ventures
and limited partnerships. The Partnership expects to meet its long-term
liquidity requirement through the sale of its communities and investments in
joint ventures and limited partnerships, and cash reserves.

Inflation
---------

All of the leases or terms of tenants' occupancies at the properties allow for
at least annual rental adjustments. In addition, all of the leases are
month-to-month and enable the Partnership to seek market rentals upon reletting
the sites. Such leases generally minimize the risk to the Partnership of any
adverse effect of inflation.

Year 2000 Compliance
--------------------

The General Partners have assessed the impact of the year 2000 issue on its
reporting systems and operations. The year 2000 issue exists because many
computer systems and applications abbreviate dates by eliminating the first two
digits of the year, assuming that these two digits are always "19". As a result,
date-sensitive computer programs may recognize a date using "00" as the year
1900 rather than the year 2000. Unless corrected, the potential exists for
computer system failures or incorrect processing of financial and operational
information, which could disrupt operations.

                                       9
<PAGE>

Substantially all of the computer systems and applications and operating systems
in use in use by TWC and the properties have been, or are in the process of
being upgraded and modified. The Partnership is of the opinion that, in
connection with those upgrades and modifications, it has addressed applicable
year 2000 issues as they might affect the computer systems and applications
located in the Partnership's offices and properties. The Partnership anticipates
that implementation of solutions to any year 2000 issue which it may discover
will require the expenditure of sums which the Partnership does not expect to be
material.

The Partnership is exposed to the risk that one or more of its vendors or
service providers may experience year 2000 problems which impact the ability of
such vendor or service provider to provide goods and services. Due to the
availability of alternative suppliers, this is not considered as significant a
risk with respect to the suppliers of goods. The disruption of certain services,
however, such as utilities, could, depending upon the extent of the disruption,
have a material adverse impact on the Partnership's operations. To date, the
Partnership is not aware of any vendor or service provider year 2000 issue that
the General Partners believe would have a material adverse impact on the
Partnership's operations. The Partnership, however, has no means of ensuring
that its vendors or service providers will be year 2000 ready. The inability of
vendors or service providers to complete the year 2000 resolution process in a
timely fashion could have an adverse impact on the Partnership and the effect of
no n-compliance by vendors or service providers is not determinable at this
time. Residents who pay rent to the Partnership do not pose year 2000 problems
for the Partnership given the type and nature of the Partnership's properties
and residents.

Widespread disruptions in the national or international economy, including
disruptions affecting the financial markets, resulting from year 2000 issues, or
in certain industries, such as commercial or investment banks, could also have
an adverse impact on the Partnership. The likelihood and effect of such
disruptions is not determinable at this time.

The General Partners expect to have all systems appropriately modified before
any significant processing malfunctions could occur and does not expect the year
2000 issue will materially impact the financial condition or operations of the
Partnership

                                       10
<PAGE>

                                    PART II
                                    -------

Item 6.  EXHIBITS AND REPORTS ON FORM 8-K

        a) Exhibits and Index of Exhibits

          (3)  Certificate and Agreement of Limited Partnership filed as Exhibit
               A to Registration Statement No. 33-23183 and incorporated herein
               by reference.

          (27) Financial Data Schedule

        b) Reports on Form 8-K

             None

                                       11
<PAGE>

                                   SIGNATURE


In accordance with the requirements of the Exchange Act, the registrant caused
this report to be signed on its behalf by the undersigned, thereunto duly
authorized.


                              WINDSOR PARK PROPERTIES 6,
                              A California Limited Partnership

                              By:  The Windsor Corporation, its Managing General
                                   Partner


                              By \s\Steven G. Waite
                                 -----------------------
                                    STEVEN G. WAITE
                                    President


Date:  February 3, 2000


                                       12