Am I doing this right?

Hi folks:
I've asked several questions lately and I appreciate your indulgence. I just want to make sure I do this right, and I'm fuzzy on one aspect.
I currently have Vista Home Premium on a single drive in my system. Since I'm moving to W7 Pro rather than W7 Home Premium, I'll have to do a clean install. I've a lot of programs and data so my approach will be to take my current C drive with Vista out, put in a new drive, load Vista on it, and then do the upgrade to W7 on that drive. Then, I'll put my original Vista drive back in as a secondary drive so that i can take my time moving data over to the new W7 installation.
I'm doing it this way so that I have a boot sector on C for W7, and a boot sector on D for Vista, so that if I have any problems with the W7 install, I can always revert to the Vista drive and keep up and running. I thought about a dual boot with Vista on C and W7 on D, but if I do that and C fails at some time down the road, I wouldn't be able to boot into D because the boot loader would be on the failed drive.
If all that makes sense, here's my question.
Back in the day, we would determine through cabling, or strapping, which drive was C and which was D. I'm unclear how that works with current systems and SATA drives. Once I'm up and running on W7 on the single, new drive, which of course would be C, and I put the Vista drive back in the system, will the system automatically assign that drive as D, or do I need to do something to accomplish that?
I saw a reference to making a drive "active" and wondered if I would have to do some designation as to which drive was C, and which was D.
Thanks.

basically install with your vista drive out.
when its all setup put your drive back in and make sure that your system is set to boot off your new drive and not the old one.

Drive letters are auto assigned but im sure you can pick where you want each to be mounted in one of the admin tools.

Only thing id be weary of would be booting your vista with the win7 drive still in.

In all honesty if you just want the vista part for recovery, id suggest just having an ubuntu live disc on hand - its always handy.