Hello there pipem90,
Heres an article about that very issue. Check out this article named iPod not recognized in 'My Computer' and in iTunes for Windows found here http://support.apple.com/kb/ts1369.
There is more to the article but start here:
1. Start with the iPod Troubleshooting Assistant
If you have not already done so, try the steps in the iPod Troubleshooting Assistant which applies to your iPod; this will often solve your issue.
If you're still experiencing the issue after going through each of the steps in the assistant, continue with the steps below in this article. The most likely solutions are listed below (for both USB and FireWire (IEEE 1394) iPod connections). Check each section starting from the top of the list to see if that is what's keeping your iPod from appearing.
Note: To determine if your iPod syncs via USB or FireWire, check the table in the Additional Information section below.
All the very best,