 What to do if your flash drive doesn't work? The first possible cause is the drive's incompatible format. Most devices support only FAT file system. Connect the drive to a computer, explore, right-click on the flash drive and click on format. Then select the necessary file system. The other possible causes is the excessive memory size of the flash drive. Create a partition with the size suitable for your device on this bigger flash drive. Go to the command prompt as administrator, enter the command disk part and then list disk. Specify its size in megabytes. Flash drive has only 2 gigabytes now. The third possible cause is that the USB port can have operability problems. Flash drive can be out of order because of various physical problems, both in the drive itself or in this particular computer.