ipod nano lost windows connection

My sons each have a nano. Their shared XP box recognized the devices for quite a while, but now does not. They may have had a bad USB connection as a root cause, but this is now repaired.

I have tried the following:
1. Updated itunes.
2. Worked through the 5 R’s on the apple site. Of course, as the devices are not recognized the restore function could not be done.
3. Used the cable to connect to another pc – the devices were recognized!!
4. Deleted Windows registry keys (at least the files, the key entries could not be removed and a default file was left).
5. Used the USB port for another device – USB port is working.
6. Tried disk mode. Still did not connect.

I’m at a loss – there appears to be a new “something” that prevents recognition on this PC.

Any ideas?!!!
Thanks!