What happens (and I've not tried this) if you assign the USB drive the drive
letter of A: under the disk management snap-in? (I'm afraid it's the only
idea that I have other than considering a USB floppy which *should/might*
work.)
Anyhow, start > run > diskmgmt.msc > highlight the USB drive > right click >
change drive letter path > set the drive to A: > press OK and close out >
does that work?