Instructions
Insert the flash drive's USB plug into an available USB jack on the computer. Try to avoid plugging it into a hub for best results, particularly a hub without independent power. Allow the drive to mount by waiting until the flashing light on the drive turns off.
Open "Computer" from the "Start" menu and identify the drive. It will be labeled "Removable Disk" and it will be appended with a drive letter. If you can't identify the flash drive, remove it again and see which label disappears. Then reinsert it and watch for the label to reappear.
Right click on the label and choose "Format...." Leave the settings at their defaults and click "Start" in the dialog box. When the lights on the flash drive turn off, remove the drive from the PC and insert it into the PS3. The drive will be formatted and ready for the backup.