Help with “full” USB drive…

I have a user that has managed to completely fill up a 1 gig USB key, jump, “whatever it is called” drive. I have tried to move files off of it, delete files and zip files but apparently, it is so full that none of these processes can be accomplished. I tried to format the USB drive but can’t using Windows XP. Anybody have any ideas how to get some of the files off of it or delete all the files or reformat the thing?? It is a SanDisk but I looked at their site and didn’t find anything that would be helpful? The user is not worried about losing any info…she just wants to be able to use the drive again.

Any assistance would be appreciated!