Please boot to the live cd, go into the terminal (click Menu, then Terminal) and then type
and press enter. Then, copy the output to here so that we can see how you've arranged your drives. Also in terminal, type
and press enter. In the top right corner of the screen there'll be a device selection menu. The menu should show one option for each drive you have connected. It should read something like (if you have only two drives):
or it may say the opposite:
If that's the case, you've installed Mint on your second drive, which I believe GRUB cannot boot to (experts please correct me if I'm wrong). Either way, please take a screen shot of the menu and post it here so we can see it.
'GRUB' is the menu that loads at boot and lets you select which operating system to load.
Good luck!