It isn't your computer. Buying a new one would be a waste of your time.

The problem is due to Windows XP Service Pack 2. I'm 90% sure. People with Linux don't get it, and the only people I've seen that get the NWN restart/BAD_POOL_HEADER bug are those with SP 2. I'm trying to find a fix for it, but I'm just saying...unless you really want to, don't buy a new computer. If you want to play NWN that badly, reinstall XP and don't download SP2.

EDIT: Ah, and don't bother with Bioware either. They're just spouting "UR COMP IS TEH SUX" over and over.