Okay, this is hardly urgent. But it's partly from curiosity and partly from fear of causing it to happen again. My new computer arrived today. After a few hiccups Windows was installed, I went about installing all the stuff I use often, games etc. The last few things I installed were, in this order:
Steam (+ Team Fortress 2, Portal)
Replaced uxtheme.dll with the VS hack
Half-Life 2, CS: Source
after which I downloaded the TF2 updates while browsing the net and sorting out my music. Once TF2 was updated it asked for me to defrag before I played. I did, then started the game. Which was when things got weird. While loading the main screen I tabbed out (not really a good idea usually but I figured it wouldn't cause me a minute of hanging like my old PC would). When I tried to tab back in, I hit a black screen. I sat there for a few minutes, hoping to wait it out. Nope. Ctrl+Alt+Del wouldn't net me anything. After a few more minutes, I figured I didn't have much choice and hard reset the PC.
Next boot, and every boot after that, I'd get through the Windows startup screen, then I'd be looking at a blank screen for maybe 10 seconds before my computer would reboot itself. I fixed it by booting Windows in safe mode and restoring to just after I'd installed DirectX. Things appear to be okay now (but I've done nothing at this point except opened Chrome).
Any idea what the hell could have caused that? I'm 99% sure it couldn't have been Half-Life/iTunes... I've been using them forever, yet I'm a little paranoid about reinstalling either right now. All I really know is that everything was running super-smooth up until that point, except for maybe when iTunes was converting files. My CPU core temps had been hovering between 31-35C.
Asus P5Q Pro
Sapphire HD4850 Dual Slot
2x2GB PC-6400 Corsair RAM
Any ideas would be appreciated.