Can I play foreign games (that aren't backups) on my US DC?
 

Can I use a bootdisc or is there a way to make it work?

Go to ####://www.gameshark.com and look in their product listings for Dreamcast. They have a disc that allows you to play imports on your US Dreamcast machine.

I thought the Utopia disk allowed you to do this?

I was uner the impression that the Utopia Boot-disc requires "NON-BOOT" discs to work. If you try to use Utopia Boot Disc with a bootable copy, it usually barfs (or at least it does when I try).