I installed linux distributions on 3 USB Keys with the software UNETBOOTIN ( with Windows XP and Ubuntu 8.10) and one with the Ubuntu program "Create a startup disk": System->Aministration->Create a startup disk. I verified that all recommended dependencies were installed for unetbootin.
My motherboard is an ASRock P4S61 which allows booting from USB keys.

When I boot from one of these 3 USB keys I receive following message :
Searching for Boot Record from USB RMF-FDD .. OK
SYSLINUX 3.72 2008-09-25 CBIOS Copyright (C) 1994*2008 H. peter Anvin

The PC does not go further. If I type on the ENTER key, I receive following message:
Could not find kernel image: linux.

Can one boot with a USB Key with a PC were GAG is installed ?
If yes, how can I solve my problem.
Thanks in advance for your help.