Can I assume that the previous OS was on one of the other drives?
It may be the issue is due to the fact that the drives were not present when win7 was installed and one is still marked as the active drive. This can lead to the Vista system attempting to start and failing due to the major hardware change
Check if you can see the drives in the bios, and make sure that the win7 drive is the active drive.
You could then try a start-up repair of the win7 system from the install media
or alternatively use an offline partitioning tool to organise the drives. The one I use is here ....
Partition Wizard is a Windows based FREE Partition Manager. It works as partition magic and supports Windows 2000/XP/2003/Vista/2008 server and Windows 7. FREE for Home and Business user.
and provides a bootable disk version that is fully win7 compatible