This is an entry from my old blog.

Have you ever faced 'Problem Ejecting USB Mass Storage Device?' while trying to eject your USB drive? You can use the same method that I posted before, to 'unlock' and 'release' any files in use in your thumbdrive before ejecting it. Usually, this problem occured if there is any video files on the USB drive, and the 'Common Task' panel is enabled in the explorer window.

First, install Unlocker, then Open My Computer, rightclick your USB drive icon, choose Unlocker. Then, choose Unlock All. Then, try again ejecting your USB drive. Unlocker works on Windows Vista.

Download: Unlocker