Computer wont talk to Router. Problem with network adapter?

Hey guys.

I have had 2 computers running fine from my safecom router, but recently i had to re-install XP on one of them, and now that computer is unable to talk to the router via the usual "10.0.0.2" However the other computer is still working fine.

Iv tryed pinging it but still nothing.

Iv tryed installing drivers for the router but still no luck.

Iv tryed chaning the ports on the back of the router.

Iv tyred using new network cable.

Also the USB ports are not working. The copy of XP i installed was not the original one that came with the computer. Could this be the problem? If so, how would i find out what drivers i need for the USB and Networking etc...?

And ideas or comments would be really appreciated.

Thanks

Scott