Insert your USB flash drive (at least 256MB) into a Vista or Windows 7 workstation, and ensure that the disk is empty.

Open a Command Prompt and enter the following commands:

diskpart

list disk     (note the disk number that corresponds to your flash drive)

select disk x

clean

create partition primary

active              (flags the partition as bootable from BIOS)

format quick fs=fat32

exit

Note: This post was edited 2010-01-07 to mention Windows 7 as a potential OS on which to perform the above actions.