Also Lian when you do find the XP cd,you can try typing "sfc /scannow" from the run command,to restore protected system files that may have been overwritten.I would try this before installing windows on top of what you have.You may want to turn off your built in LAN adapter if you have one.Sometimes an active setting in bios may cause an error that has a hardware change symptom.Update all usb device drivers that you have.And welcome to Techzonez.Let us know what you find.