Erm, maybe windows is too resource intensive for it? You might want to look into using a more lightweight OS than Windows. Like, Puppy linux.

http://puppylinux.org/main/Overview%20and%20Getting%20Started.htm

With a CD or USB, you can just run it from that and do normal browsing, while still being able to reach files on the HDD, I believe. Or you could do a full install.

I have the same computer, with the same problems. The computer overheats when running windows, and if the OS was preinstalled then it will be major trouble switching OS. I can only suggest ether switching OS, or buying a new computer. My laptop currently runs ubuntu.

the bottle neck is your processor. see if you can change it out for a better pentium, or maybe if you're lucky, a core 2 duo. you have the intel X3100 if i'm correct? go to this site: http://9xxssf.info/ . Find the correct modded graphics driver for windows vista, download, follow the instructions and if done correctly, you could have 250-350 mb of graphics memory. it's not much, but combined with a better processor, you should be able to play L4D2 at 16 25 fps.

I was in your situation, till i said, "f*** you compaq, i do what i WANT!" (and upgraded my pc)

Well, as crappy as your computer is, my computer is most likely worse. My phone has specs on par with it. Its really sad. Honestly, if you have like $200 to spare, I recommend the Nexus 7. You can browse the web, and it has amazing hardware for the price. You won't regret the investment. That is, if you don't mind tablets. So, maybe consider selling the laptop for as much as you can, and see what you can do from there?

Maybe it's a failing power supply?