i have two hard drives, and i was wondering what happens if i put them both in at once? does it prompt me on which hard drive i want to boot up? they both have OS by the way. or can i run one hard drive and access it on the my computers window? and also, on both of my hard drives i have a c: drive and a d: drive, and im wondering if i can just combine them into just a c: drive with all the space.