The Vista bootloader and the Win 7 bootloader are the same.
I can't answer your question but my guess would be that the boot files on are on the Win 7 hard drive, if it's the latter install.
I'd probably just install EasyBCD on the Win 7 drive...and then see if it automatically recognizes the Vista install. If not, then manually add the Vista install to EasyBCD, making Win 7 the default. That should (IMO) ensure that Win 7 remains bootable. Then just format/remove the Vista drive.
A simple way to find out...is to temporarily detach the Vista drive...and see if Win 7 boots. If it does, the files are on the Win 7 drive
Edited by hamluis, 01 February 2013 - 11:55 AM.