Partition error message in upgrade or clean install of RC1

I have been running Vista Beta 2 on a separate hard drive in a dual boot
configuration with XP without any problems. When I try to upgrade to RC1 I
get an error message that says, "Cannot locate the partition for installing
windows" and the system does a rollback. This occurs after files are copied,
gathered, etc. and I have received the same error message whether I choose to
upgrade or allow a fresh install. I boot into Vista to try the upgrade path
because I do not want to replace XP yet. Is there something I am missing or
doing wrong?

Thank you in advance for any assistance or suggestions.