All drivers stop working after connecting lan cable

Hi all, i did installed on a old Compaq pc last week Windows SP2 but before formatting it was XP(no Service Pack), then yesterday after connecting this pc to my other pc with a lan cable, the Xp them screw up, and after rebooting, no drivers load at boot, i tried uninstalling all the drivers then reinstall back but nothing, plus the XP theme has dissapeared, so do i need to reformat that pc or this one doesn't support SP2, cause when re-installing the drivers(made by backup with Driver Genius) i'm warned that those drivers hasn't got numeric signatures but i continued the install anyway.

I can't be a virus cause nothing was connected to that pc after the new installation

Thanks in advance