Along with each hotfix that Windows installs, you get a couple of bonuses - an Add/Remove entry for that hotfix and a folder containing the file required to uninstall it. Upgrading to Windows XP SP2 clears out the Add/Remove entries, but leaves the folders behind. You may have 60 or 70 folders in the 'C:\windows' sub-folder with names like '$UninstallKB823559$', which can take up a considerable amount of hard drive space.
After upgrading to Windows XP SP2 you can safely delete all of these folders and files from the 'C:\Windows' sub-folder except for the '$NtServicePackUninstall$' folder. This folder contains the uninstall information for Windows XP SP2.
The uninstall data for Windows XP SP2 resides in a folder named '$NtServicePackUninstall$' in the 'C:\Windows' directory. This folder in itself takes up around 400 megabytes. Microsoft does not recommend that you delete this folder as you will give up the possibility of uninstalling SP2. But if you are 100% sure that your computer is compatible with SP2 you can safely delete this folder also to free up the hard drive space. You can then go to the 'Add/Remove' list and click on the 'Remove' button to delete the entry from the list. Just remember by doing this you will no longer be able to Uninstall SP2.