Sounds like you scanned the drive at some point. You should be able to remove the drive from the Music > Location node.

I have a 132 gb flash drive that i use to play my music in the car. i manually sync it. However, right now, the songs from my flash drive are showing in my library, even though i have removed the flash drive AND rebooted the computer. Any suggestions?

BTW - they wont play, of course, because they are not there!