Try this:-
(Assuming you have some restore points saved)
1. Get a copy of Hirens Boot Disk or ERD Commander and reboot using it.
2. Open a windows manager from the boot cd and go to c:\windows\system32\config
3. Rename the following: system to system.bak, software to sotware.bak, default to default.bak, SAM to SAM.bak and SECURITY to SECURITY.bak.
4. Navigate to c:\System Volume Information\_Restore.
5. There you will see your restore points.
6 Pick a restore point from before you installed sp2 (probably a few back as you have installed patches as well)
7. Select and opt to"copy" the following files:- system, software, default, SAM, SECURITY.
8. Navigate to c:\windows\system32\config and paste the files there.
9. Reboot the system from the c drive (not forgetting to take out the boot CD.
10 Jobs done go for a coffee (or beer)
11 Remember that you now no longer have SP2 fitted !!
ps. As soon as it boots up Ok...Save a new restore point! !!