XP Networking problem -Help required fast

Hi,
I have windows XP pro as does my brother recently I setup a network and its was fine. then it just gave up working, said there was corruption with me WMI information or sumin like that, so I reformatted and it was fine and now its just done it again. Is it sumin im doing when im tweaking my pc, is there sumin i can do without reformating my hard drive again and get the network connetion to wrok? His computer connects to the internet via mine, my connections is 112k broadbnad(Poor i know but im a student bum). any help would be greatly appreciated.
DoM

It might be something you are doing.
It might be hard drive corruption.
It could be a virus (at least theoretically.)

Hard to tell on the info you provide;

First thing to do: run at stock speeds for a while and see if it still happens.