I have a Sandisk Cruzer 2GB flash drive that indicates that there is 1.67GB worth of files on it when there is nothing showing on it. What in the world is going on here? I only have 237MB worth of storage space.
1) Make sure you've emptied your Trash (with the thing plugged in and mounted). Just putting something in the Trash does not delete the file, nor allow it to show as "available" space. (I forget this all the time.)
2) Set your file manager to show hidden files and see if there's anything there.
EDIT:
It's been while since I've been around a Windows machine, but I think Vista onward can use USB drives as an extra swap file. Make sure that is NOT the case.
Alright, I figured it out. Apparently it had "ReadyBoost" running and it was acting as an extension of RAM for my computer, I guess. I turned it off and now it is ready. I also reformatted it as stated above. Thanks everyone.