If I'm getting your question correctly, you wish to change which drive the computer is booting from, correct? In that case, it should be pretty simple. You'll have to have your computer off, turn it on and it should prompt you to press a certain key to go into your computer's BIOS. I'd guess what the key is but I've seen so many you'll just have to check (Mine is the DEL key). After you get into your BIOS you'll need to look for something called something along the lines of "Boot Order." All you have to do is edit the boot order to put the drive you want to boot with on top. Restart the computer and voila!