I have a curious problem that the internet so far has not cracked. All 3D-accelerated graphics (not DirectX specifically) run in slow motion. Framerate is about 2/3. Everything from complicated cutscenes in LA Noire to the window animations in Explorer will run at this slow rate. Team Fortress 2 however won't go slo-mo, but it does drop frames constantly. It drives me insane - and naturally causes audio synching problems.
I'm running a reasonably up-to-date setup (see below), but my card is a bit older: PNY GeForce 9600GT with 512MB of GDDR3 memory. I've never had trouble with it before, and while I intend on upgrading long-term, its served my purposes fine so far.
Some inspection with GPU-Z tells me all my card's processing frequency's (i.e. core, memory, shader) are all at 0MHz. Which is odd.
I originally was using the latest nVidia drivers, but then rolled back to Microsoft's 2009 drivers. Briefly fixed the problem, but now it's come back. And here I am.
Discovered cause of the problem: AMD's Cool & Quiet CPU throttler was causing a massive bottleneck and basically excommunicating the video card. Disabled it in BIOS, and now everything works perfectly. I don't get why they even enable throttling on desktops...