Formatting a flash drive that has EFI using Windows 7.
Start -> Run, type DISKPART
DISKPART> list disk
Find the disk you want to reformat, and select it with the appropriate number,
DISKPART> select disk 1
Once selected, you can delete the GPT / EPI by the clean command:
When complete, you can proceed to format the disk the traditional way through
disk management and selecting FAT32 or NTFS.