Half-Life 2 (plus episodes) have a tendency of crashing my computer

Solution 1:

Simply being able to periodically let your graphics card "rest", and the problem goes away, is a pretty clear cut case of a heat related issue. Being a notebook, it's tough to tell if dust is encasing any of your hardware, even if plenty of air still seems to be flowing out of the holes. Every notebook I've ever had has seemed to "heated up" with age, and the particular processes HL2 (and the particular graphics settings) may make this particular game more susceptible.

I used to laugh at people that played on "cooling pads", but I've got a coworker that can now play Sims 3 at three times the frame rate she was getting before she bought it. It might also be worth a try to physically open the notebook, get to the motherboard (assuming an onboard chipset), and clear out any debris you see.

If it's somehow a strange cache-related issue, there won't be much that you can do short of driver updates and tweaking graphics settings.