if you hit delete as the pc boots you can get into the bios and check that usb support has not been shut off. I know you cannot use the usb devices in windows but a pc without ps2 mouse and keyboard connectors does liven up the usb ports from switch on, it is only windows, that has it turned off. Do you have a startup disk? If you start with a floppy assuming your pc has one you can use system restore to go back to before the problem. If all else fails do you have an xp sp2 disk as issued by pc advisor? and others. If so run the sp2 setup and on rebooting you should find the usb devices live again.