When I tried to connect my iPod to my nice new Vista machine Windows wouldn't recognise the device at first.
A quick search on the web and I found this page which fixed it.
Basically, reset the iPod and then connect it again.
To reset toggle the hold switch on and off (Slide it to hold, then turn it off again), and then press and hold the menu and center buttons simultaneously until the Apple logo appears (takes about 6 to 10 seconds)