External HDD connectivity problem

Hi all, I have an IO Data 160GB external hard disk drive that connects to my laptop PC via the firewire (IEEE 1394) port. My problem is that my pc is no longer recognising the device, (it worked before) I have tested this drive on a friends computer and it works without problem so I know that the drive is functioning. I also borrowed a friends external HDD that connects via the USB port and my PC did not recognise that either. Thus the problem would appear to be software related. I am guessing that this is a windows problem.
Can anyone with greater understanding of how windows interacts with such devices suggest a course of action? Much appreciated. My specs are:

Windows XP Professional
Fujitsu Amilo D 997MHz Laptop Computer
256MB RAM

Alex