I learned to format my 2gb flash drives on Disk Utility by clicking the Erase tool bar and choosing volume format to MS-DOS FAT. I did this because I was assuming I can use my flash drive on PCs as well. As I was using my now formatted flash drive on a Windows PC, it was suddenly not recognized and needs to be formatted by Windows. Luckily, I had a spare 2gb flash drive with the same files in it. Then, I found out that the default format for Windows PC to recognize the flash drive is FAT16. I really didn't thought that MS-DOS FAT when Erasing a.k.a. formatting the drive in Disk Utility wouldn't work on PCs. This is the same with NTFS formats that Macs can not overwrite. I suggest that to be able to use your flash drive on both Macs and PCs, to format it first on windows so there will be no problem for windows recognizing it. But then again, is there an application in OS X that would format any drive for PCs to recognize it immediately?