How do I make a dual boot/dual disk system? (t61p)

[Oro]

Here is what I want to have running (have all the hardware):

Internal drive with 128gb SSD, running Windows 7 (or 8 )
Ultraybay caddy with SATA HDD (500gb), running Windows 7 or 8 (may upgrade to play with it)

The idea is the ultrabay drive is for storing pictures and data, and as a back-up if the main drive fails - eg., it's bootable and I'd have a an immediate mirror of my main drive for all intents and purposes, no real down time. My first attempt at this failed. Everything seemed great and the SSD was working peachy, but then with both drives in, windows decided to ignore the Bios boot order I had and it booted from the ultrabay drive. From what I could tell, it realized it was a clone of the main and bricked both - disabling windows on both drives so I was blocked completely. Fortunately I had the machine's original 100gb drive elsewhere and I was able to get back my data, though after many hours, and reinstall 7HP/64 on the SSD and have it running nicely. I thought since I was just making a copy of Windows for back-up and it was in the same machine, that was OK (ignorant me, I guess MS hates that and punishes you badly for it).

So, what do I need to do if I want to accomplish this? Do I need a different version of Windows (I have 7HP, maybe another 7 version allows multiple home installations, or more than once on the same machine?)

I have the option for a small fee to upgrade to 8 (from a 7 purchase this year). I understand that lets you upgrade to 8 "Pro" - does that give me the flexibility to do what I want, e.g. - more than one installation, vs. the 7HP I have been using? Or is what I want just not practical with MS OS?

[twistero]

Just shooting in the dark here, but since you cloned the drives, they would have the same partitions and more importantly, duplicate partition UUIDs. I guess Windows does not like that.

[Oro]

Honestly, I don't know what UUID's are (just read the definition now, never heard of them before).

My intention was to use EaseUS Partition to go to the 500gb drive and change partitions. So perhaps if I had put it in the internal slot, booted from it, then re-arranged partitions, then put it in the ultrabay and the SSD back in the main, it would have worked?

I can understand MS doesn't want people to just clone drives and hand them off to another machine. I'm only looking to have a bootable second drive in my single machine if that's possible.