If hotfixes have been applied to Windows NT, Windows 2000 or Windows XP, that is
recorded in the registry. Check the following registry key to see what hotfixes
have been applied. This is how utilities can query the OS about which hotfixes
have been applied.
There will be a subkey for each hotfix that has been applied. This registry
tip applies to NT, W2K and XP.
Freeware utility Hotfix Control uses this info to keep track of what hotfixes
are applied, and when they were applied. Site says its for Windows NT but as far
as I can tell it works fine for W2K and XP also.
Microsoft' utility Network Security Hotfix Checker ( HFNetChk ) is a command-line
tool that enables an administrator to check the patch status of Windows NT 4.0,
Windows 2000, and Windows XP machines.
St Bernard's product UpdateEXPERT is a software patch vulnerability assessment tool
that scans your networked systems for missing patches and remediates discovered
weaknesses for increased protection. UpdateEXPERT features an extensive database
(including service packs, hotfixes and other patches) that is maintained by St.
Bernard Software's software patch experts.