Vista Installation Key "Mileage"

Hi guys, here's the issue I'm looking at.

1)I own a gateway that's around 2.5 years old, it's been a decent system, I've done a number of upgrades to it, but the motherboard's starting to have some capacitance issues, and the machine is no longer under warranty. Due to this, I'm considering upgrading the motherboard and cpu to something quite a bit more modern in the next month or so. Right now, I have an installation of Vista 32bit Home Premium.

2)I'm already aware that I don't simply own Vista Home 32bit, but rather the Vista Home serial key that came with my computer. If I want to (I do), I can order an installation disc (Gateway didn't include one...thanks) for the 64bit edition instead, and perform a clean install on my machine.

3)Here's what I mean by "mileage," I simply want to know what upgrades I can make to my machine before I go ahead with the 64bit Vista installation, and still be able to use my current key. Will a new mobo/cpu render this Vista key useless no matter what?

Back several years ago, I actually upgraded nearly every component of an old computer of mine, save for the hard drive with WinXP installed on it. I was locked out of windows of course, but MS was fine with letting me go ahead with an over the phone activation in spite of all the new hardware. Should the situation still be the same today?

Note: I'm aware that the issue here doesn't really have *anything* to do with upgrading to 64bit over 32, it's really a question of "how far will my windows key take me" and nothing else really. Before anyone chimes in, I'm fully aware that I can't just "upgrade" to 64 from 32 and will need to do a clean installation. Thanks for the read!