dsl on a thumb drive

I recently attempted to load DSL Linux on a thumb drive setup with virtualbox(oracle) portable. (windows xp is host)
I was able to install onto the virtual drive. Partitioned within the virtual hard drive a bootable Linux drive. Install went great. However when all said and done it won't boot on the disk. The reason I went this way is that I am practicing with vi during down time at work, so I was hoping to have an all in one box. It will boot fine and run from the ISO file. However it does not like to without the ISO being present.