Well to be honest it seems like a motherboard problem most likely. When you put the other hard drive in another computer and tried to boot off of it, it's natural to get bluescreens. You can't just go switching hard drives on operating systems.
Well in both cases, the hard drive being broken or the motherboard being broken data recovery is your first step.
Put the hard drive in another computer, set your hard drive as SLAVE and make sure in the BIOS it is not set to boot from your hard drive. When you do this properly their is no reason for you to not boot off of the other hard drive, so you can get your files.
Step 2 is prevention.
Get soemthing like this
This also allows you to put your "bad" harddrive in here and read it from any computer without opening up the case, just plug your hard drive in.
Than get a harddrive for it (or 2, if your current one is dead)