It shows up when I plug it into a Vista 64 bit machine, not though when I plug it into a Windows XP (32) SP3 machine. Any ideas? Thanks.
Go to Settings/System Settings/USB Mode and change it to MSC. It should show up as 2 flash drives, one for the unit and one for the microSD card slot.
To be recognized in MTP mode it needs Windows Media Player 10 or 11. The original XP came with WMP 9, so check the version and see if it needs to be updated.