if system restore is disabled then y ou don't have any restore points to restore to because when you turn off system restore it removes all of your restore points....therefore....if you do turn system restore on...you won't have anything to restore to...you should probably try to do a repair installation of windows..
Boot up with the XP CD in the drive and let Setup run. Go past the "C" and "R" repair options by presssing Enter just as if you're doing a clean install and you'll eventually get an option to "Repair an existing installation". That's the one you want. If it asks about formatting you've gone wrong, so start over.
You'll get to keep your existing apps & settings, but you need to re-install SP2, Windows Updates & any unsigned drivers afterwards. NOTE: Be aware that you'll lose any protection from Blaster / Sasser type worms. Don't go online without a firewall, whether the built in Windows one or 3rd party.How to Perform A Re-Install Of XPRepair XP