Go to Start|All Programs|Accessories|System Tools|System Restore. Tell it to
"Restore to an earlier time" and click Next. Click on the bold dates in the
calendar and the right hand box will tell you why that restore point was
created. Do this until you find the one where the right had box says that
SP2 was installed or until you run out of bolded dates, whichever comes
first. If you run out of bolded dates first, the restore point from the SP2
install is no longer on your computer.

If you roll back to the SP2 install, it will uninstall SP2, you'll probably
want the first restore point after the SP2 install.