
Some of the reasons why the problems occur are :
- You use the Safely Remove Hardware feature in the notification area to disconnect the iPod. Then, you disconnect the USB cable.
- You use the Eject command in Windows Explorer to disconnect the iPod. Then, you disconnect the USB cable.
Although the above two reasons look very obivious that you follow. But strict following it would be better.
Do have a look at this KB article at microsoft and also download the update provided by Microsoft for your Vista.