if u have windows 98 u have to add the proper driver for ur bd
if u use w2k or wxp, its included. in this situation u have to see the port is not obstructed ( there are share usb ports and maybe u use it from the other output with some device)
if not, u must know there r incompatible devices too. if its a simple disk on key, throw it. if its something more serious look for a board upgrade