If you want to have windows 8 on another disk then you essentially have two different NTFS file structures. eg. if you install WoW onto windows 7 SSD and lauge of Legends onto windows 8 SSD you will not be able to play WoW from windows 8.
What I think you are looking for is a Dual boot configuration, one drive two operating systems shared NTFS storage. Google up dual boot configuration there is thousands of walk-through's.