Whenever MS updates something, i.e. 'critical patches', 'hot fixes', 'security updates', etc etc, they appear in Control Panel, Add or remove programs. That's fine, it tells me something was installed, allows me to uninstall it if it proves to be a dud. The necessary downloaded files appear in C:\Windows\SoftwareDistribution/download/cfe8c........ and numerous other subdirectories. A sort of uninstall executable for every one of these goes in C:\Windows\$hf_mig$\KB904942 and dozens of similar directories. The uninstall program is identical for most of these. Then the actual dll's or programs also go in C:\windows\system32 and likely many other places too, like pre-fetch. The original versions of these dll's etc (for uninstall reasons), go into C:\windows\$NtUninstallKB904942$ and a few dozen similar names since SP2. The 'ready for install' files with a abbreviated suffixes into C:\i386 such as taskmgr.ex_ I'm annoyed that the vast majority of these are totally wasting my disk space and lengthening the time it takes to create an image of the O.S. Let me tell you what happens after install of SP3. First off, nearly all the KBxxxx are redundant, since they are replaced in the service pack, and helpfully, they disappear from 'Add remove programs', but not from all the other places. At the very least, all the original download files are completely useless, since they have been unpacked into other places such as C:\Windows\$NtServicePackFiles\i386. A quick estimation tells me that very nearly one Gigabyte of data is completely surplus to requirements following SP3. As an exercise, and assuming you have set your PC to show hidden and system files, try a search for 'taskmgr.e' You should find it in at least 5 places. I always zip up and delete the whole content if C:\i386, storing it somewhere else. I can restore it if I every need to uninstall something. Following the installation of SP3, amazingly, the whole of C:\i386 is now full of the original XP files of August 2002. I give up!