My laptop hasn't felt "right" on various games in about a month, and today my framerate on Counter Strike: Global Offensive was just appalling, which I had attributed to a recent patch or something like that. I then jumped on World of Warcraft to fight something with Sabriena, and noticed a poor framerate (~20FPS) there as well. I tabbed out to check something, and the Nvidia "performance" GPU crashed, leaving me with the heinous Intel integrated monstrosity.
I went to check for new drivers, and the entire PC crashed... blue screen. I haven't seen one of those in ages on this machine (Sabriena's desktop did it a couple of days ago).
I then noticed the entire bottom of the laptop was rather hot, and so I cracked into it to check for dust. Sure enough, the entire heatsink was absolutely caked in dust. Damn it.
After cleaning it out and reassembling it, World of Warcraft is up around 60~70FPS, which is where it was when I first got the thing. Much better - I guess I better start making a habit of cleaning it out every 6 months or so.