Here's a couple of links that may help you...
http://www.howtogeek.com/howto/linux/cr ... -easy-way/
http://www.blogsdna.com/3002/create-ubu ... indows.htm
If you already have it installed on the flashdrive, then it may be you just need to boot into Ultimate Edition, plug in the flashdrive, start 'Partition Editior', select the flashdrive, right click on the paftition, select 'Manage Flags', and check 'Boot'...