Let's see. Try reformatting your iPod to FAT32 in Windows, followed by a restore in iTunes. To do that, follow these steps:
1 - Connect your iPod to your computer.
2 - When iTunes has finished syncing with your iPod, open "My Computer".
3 - Right-click on your iPod, and click on "Format". (If your iPod is not showing in My Computer, make sure that
disk use is enabled in iTunes).
4 - Here, verify that your formatting settings are "Default", with the format type set for FAT32. Also, make sure that "Quick Scan" is not selected.
5 - Then, click on "OK" to begin the formatting process.
6 - When this is complete (it might take a while), make sure to restore your iPod in iTunes again, so as to properly reload the firmware back onto it again.
If that didn't help with your problem, then you could also try assigning your iPod a different drive letter, following the instructions from this Apple Knowledge Base article:
Windows confuses iPod with network drive or hard drive
Any difference after you've tried those two things?
-Kylene