Handy CLI tool, part of XP OS:  MSIZAP.exe.  Just enter "msizap"
at the command line to get the Help:

C:\Documents and Settings\Thnikpad>msizap

Copyright (C) Microsoft Corporation, 1998 - 2001.  All rights reserved.
MSIZAP - Zaps (almost) all traces of Windows Installer data from your machine.

Usage: msizap T[A!] {product code}
       msizap T[A!] {msi package}
       msizap *[A!] ALLPRODUCTS
       msizap PSA?!

       * = remove all Windows Installer folders and regkeys;
           adjust shared DLL counts; stop Windows Installer service
       T = remove all info for given product code
       P = remove In-Progress key
       S = remove Rollback Information
       A = for any specified removal, just change ACLs to Admin Full Control
       W = for all users (by default, only for the current user)
       G = remove orphaned cached Windows Installer data files (for all users)
       ? = verbose help
       ! = force 'yes' response to any prompt

CAUTION: Products installed by the Windows Installer may fail to
         function after using msizap

NOTE: MsiZap requires admin privileges to run correctly. The W option requires t
hat the profiles for all of the users be loaded.

C:\Documents and Settings\Thnikpad>msizap g!

MsiZapInfo: Performing operations for user S-1-5-21-3133328356-3430417406-237525
0919-1004
Removing orphaned cached files.
   Error opening 8A0F842331866D117AB7000B0D610001\InstallProperties subkey of Pr
oducts key for S-1-5-18 user. Error: 2.
   Error opening CABF2C13FC763904F863511A64167374\InstallProperties subkey of Pr
oducts key for S-1-5-18 user. Error: 2.
   Removed file: C:\WINDOWS\Installer\87477d9.msi
   Removed file: C:\WINDOWS\Installer\10b6dedf.mst
   Removed file: C:\WINDOWS\Installer\18e1d.mst
   Removed file: C:\WINDOWS\Installer\18e1e.mst
   Removed file: C:\WINDOWS\Installer\18e30.mst
   Removed file: C:\WINDOWS\Installer\18e31.mst
   Removed file: C:\WINDOWS\Installer\1a424.mst
   Removed file: C:\WINDOWS\Installer\1a425.mst
   Removed file: C:\WINDOWS\Installer\1a426.mst
   Removed file: C:\WINDOWS\Installer\20b8b.mst
   Removed file: C:\WINDOWS\Installer\20b8c.mst
   Removed file: C:\WINDOWS\Installer\20b8d.mst
   Removed file: C:\WINDOWS\Installer\67b8d14.mst
   Removed file: C:\WINDOWS\Installer\67b8d17.mst
   Removed file: C:\WINDOWS\Installer\979c1.mst
FAILED to clear all data.

--- Thunderbird 2.0.0.24 (Windows/20100228)