Chredge

Hi All, Hope someone can help me here. All of a sudden all 6 USB connections on my desktop XP had stopped working. The computer itself is fine and boots up without a problem it's just so damn annoying that my USB keyboard and mouse don't work now because of this. I've tried uninstalling the USB drivers from Device Manager and re-booting the PC in the hope that Windows may re-install these again on startup but this doesn't work. I gave up and bought a PCI card with 4 USB connections in the back. I installed the card and this worked fine (while the machine was switched on...). The next day I switched on the PC and the USB connections had stopped working again. I removed the USB PCI card from the PC before re-installing this again and rebooting. When the machine started the card was working fine again. I am now too scared to switch the PC off incase it 'forgets' about my USB PCI card and I have to go through the whole process again. How would I resolve this issue? Hope you can help, Chredge.