help with a flash drive

i have a 4gb flash drive. i want to copy a large file onto it (348 Mb). it says the flash drive only has 87 mb free. there is nothing stored on the flash drive besides a file called launchU3.exe which was on the drive when i bought it and i it wont let me delete it ( i think its there for windows interface thing). question, could it be that there are hidden files which i cant see and are taking up space. there should be plenty of room but there is not. thanks