I haven't had the "pleasure" of fixing a Windows install for a while, but tonight I was helping a friend fix their PC.  Apparently Winsock2 got corrupted on their system somehow, I suspect some web browsing spyware... Services that I've never seen fail were failing, things like DHCP and NETLOGON.  I installed the XP support tools from the XP SP2 CD and ran netdiag /test:winsock.  That of course produced a nice fat error, which prompted me to run netsh winsock reset.  After doing so the system started behaving much better and I was even able to get on the internet and login to the system without crashing.

MS KB Article that helped me 811259