Guys u can simplly delete all the $NTUninstall$ folders. they are uninstall data for hotfixes and updates thru automatic update service and service packs.
I dont think anyone uninstalls these hotfixex

or do u?
I always delete them.
Another location u can empty is windows\system32\dllcache (it is a hidden folder) This folder contains extra files from the XP setup CD. These files are basically the drivers n stuff of all kinds of hardware and software u dont have installed. so then when u plugin a compatible new hardware the drivers are picked from here. If you delete these files the worst that will happen is when u add that hardwre/software then windows will ask for the 'windows XP setup cd'. I always delete this too. Because i keep a iso image on my hdd of my *licensed* windows XP CD. so i pop this iso into a virtual drive when needed.
And if u want to delete system restore files do that thru system restore itself, leave teh latest save point intact. this will free a lot of space.
So you can remove them. but as the wise always say - "At ur own risk".
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TIP: before doing this manual disk clean up you should always check "Hide protected operating system files" under folder options.
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Happy cleaning. Dont forget to wash hands afterwards