Temp folders are in C:\Documents and Settings\User Name\Local Settings\Temp. The c:\windows\$ directories are backups for hotfixes and security patches.
If you haven't already ...disable hibernation ...Ctrl Panel>Power Options>Hibernate.
Delete all of your Hotfix backups ie. $NtUninstallKB885835$ stuff ...it's recommended that you have a backup image of your hard drive before you do (preferably stored on another hard drive on your network or some other removable media) ...just in case and especially if you turn off restore. I've only had one occasion to uninstall a hotfix that was in fact, documented by MS and a subsequent hotfix soon became available.
Also, you can delete your driver file backups and certain other program backups that may not have gone into "temporary" folders, in other words "other" download locations.
You can tailor back those items in WinXP that you may not need like Games, MSN Explorer, Internet Information Services, Mgt. and Monitoring Tools etc... ...Ctrl Panel>Add or Remove Programs>Add/Remove Windows Components.
You can tailor back programs and features that you don't need in Office ...Ctrl Panel>Add or Remove Programs>MS Office and select "Change".
Download
CCleaner to cleanup your index.dat file and other residuals left behind by certain programs like Adobe, Ahead Nero, Quicktime, Realplayer, Windows Media Player, DVD Shrink, Sun Java, Google Toolbar, Ad-Aware, Alcohol, MS Mgt Console, MS Office etc... It's convenient and free. Also, run it's registry cleaner to get rid of unwanted registry entries. This is especially useful after you delete all of your hotfixes and patches.
Right click on your C drive, select properties and select disk cleanup. See if the diskcleaner wants to compress any old used files.
Added:
I usually find between 3.25 GB and 4.5 GBs on my installs including Office and a modicum of programs ...no games.
