You'll either have to ask sony to send you new media (not free, and sometimes for old PC's they may not have the media available anymore, particularly now that XP home is officially not supported anymore by m$), or if you can still boot into the OS, you can check the installed sony tools, you might be able to burn recovery media if there is a recovery partition on the PC, or again if there is a recovery partition on the PC you can use that to restore the PC to factory defaults, or your last chance is to buy a new OS.
