Frustrating issue.. need expert help

[snwtoy]

Whenever I follow the instructions to create a bootable Vista installation UFD, or WinPE 2.0 ufd, the following occurs:

Computer stops on the dos screen just after post, with a flashing cursor and nothing else.

Have had the same result from 3 different pcs all configured to boot from usb.

The UFD is a Jetflash Elite 4GB. I have had this working in the past, but had to reformat the key at some point and now cannot get it to work again. Driving me crazy!

I have tried all manner of formatting tools, bootsect.exe commands, etc, but nothing seems to work, always end up with the same situation.

I know the key still works fine - I can boot to fat32 dos using the HP utility with win98 boot files.

Am going to see if I can get bootrec to write a new mbr to it, but that's my last hope.

Any other suggestions?