You really, REALLY should install SP3 on XP. Some of the commands I use and controls, use some API calls that where available in XP SP3 and newer versions of Windows.
But besides that, MS had put in a LOT of performance enhancements and bug fixes in SP3, not to mention the insane amount of updates AFTER SP3.
I havent tested my windows repair in SP2, I only tested it in XP sp3, so it is possible the installer also needs SP3, again I never checked on SP2 for that. So you could download the portable version and extract it and try that.
May I ask, why are you still on SP2?
Shane