I've explained this already: the crack works fine. Played quite a few hours on XP with SP3. Also works fine on Vista SP1.
From what i read in the official sys requirements, the game should work fine on XP with SP2.
http://www.yougamers.com/gameometer/10335/
Update drivers, DirectX and, why not, run the Windows Update and install SP3. The game has a normal protection, involving CD-checks, so no intrusive c..p. I think it's a problem somewhere in the OS or dirvers area, or maybe something in the PC doesn't meet the minimum requirements.