Computer turns off upon login

I've been having a lot of issues with my new build where instead of getting nice friendly error messages, the computer just turns itself off after Windows 7 starts. I don't mean that it triggers the shut-down process, I mean it just dies, on the spot, as if I pulled the plug. Love the new error handling in Win7, really, it's top notch. :-p

For example, one issue seems to have been an incompatibility with my video card's audio device (it has an HDMI port) and the motherboard's audio device. Fine, I disable the video card's audio device and it seems to be happy.

Anyway, after reinstalling Win7 for the 3rd freakin time, I'm now installing one "thing" at a time, rebooting, playing around for a few minutes and running some tests to verify stability, then moving on to the next "thing". I define a "thing" as a single driver, a single Windows Update module, or a single application.

Things have been going a little better, as I got all the major drivers and updates installed, but the latest issue baffles me: Launchy. After installing Launchy (if you've never heard of it, it's a simple keystroke program launcher, nothing too fancy), the computer once again turns itself off after login. Launchy? Seriously!? Is Win7 this damn unstable???

OK, OK, calm down.

No biggy, right? Just go into safe mode, and take Launchy out of the startup folder. Done. Whew. Problem solved, at least for now, right?

Well...no. Still dies upon login. WTH?

Looking at msconfig via safe mode, there are no launchy-related items being run upon startup.

Alright, fine, I'll just uninstall in while I'm in safe mode -- but wait, apparently you can't uninstall things in safe mode. Whose brilliant idea was that!? :-ppp

So, what can I do to avoid having to reinstall this god-forsaken operating system a fourth time? Any suggestions?

Thanks in advance,
D