System32\DRIVERS\PCI.SYS is either corrupt or missing?

my computer says "system32\DRIVERS\PCI.SYS is either corrupt or missing" its not a hardwhere problem as I have not put any new parts in. It randomly did this to me one day. It says push "r" at the first screen to attempt to repair by putting in a windows XP disc. I push "r" and the disc is in but it just goes in this annoying loop to the dell starting screen to that error message. The only other options are F2=setup F12=Boot Menu Ive looked through both of these and nothing helped.