First it was Civ V, which kept giving "incomplete installation" errors. After two redownloads and a lot of wasted time I narrowed it down to a problem with Avast! antivirus. That was also the cause of the 15 minute loading screens.
Then it was Homefront, which liked to crash during the intro cinematic. Eventually I fixed that with something or other with forcing it to use DirectX 9. Then it decided to crash partway into the last mission, conveniently before a checkpoint so I had to rewatch a whole lot of scripting every time I tried a solution. Somehow disabling cutscenes fixed that.
Now it's Fallout 3. It likes to crash when I'm in the Wasteland. 90% of the time it takes the form of Fallout quitting, with no error message and none of the usual symptoms of problems such as a hard drive that never stops or anything "not responding". Sometimes it seems to keep playing, so I can still shoot and possibly move and turn, with NPCs still doing their thing, which I can tell from the sound, but the screen is frozen. Hitting escape crashes it. And then there is the one where it has the animation of a window minimizing, but frozen halfway down the screen, gives no error and is still in the task bar, but is obviously not able to be played. Tabbing out causes it to crash and give an error.
I've tried all sorts of things with the common solutions: video drivers, multi-core fixes, sound somethings. I did seem to get some respite by not using quick-saves, but that was not a complete fix. Auto-saves were kept off.
So my review of Fallout 3 so far: It's like Elder Scrolls: Oblivion with guns, which is pretty fucking awesome, except it crashes all the time, but only outside.
I'm considering getting Windows 7 if only to know that I have a perfectly clean, fresh install that knows how to use hardware and software newer than 2005. But that's at least $120 for debatable utility.
 I had tried lowering my video settings earlier, with no apparent benefit. A second attempt seems to have helped somewhat. What is the point of a game auto-setting video settings if those settings are going to cause it to crash?