The Bloke On Who Wants To Be A...
Film, Media & TV2 mins ago
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For more on marking an answer as the "Best Answer", please visit our FAQ.There's no way to restore a system in the way you suggest, unless you took regular registry backups, and even then the restore would be flawed. I think the best you can hope for is a repair of Windows by booting from your Windows XP CD and choosing to repair the installation (the SECOND time it asks, not the first time with the recovery console).
With a non-legal copy of XP however, you're always going to have trouble with service packs. Might be time to open the wallet, maybe?