I have two computers in my room running CS:S, one max settings and one mid range with high shadowing. The one that runs it at mid range settings does so perfectly and is faster than I expected it to be. It only cost me about 20$ and a little time to work on it. That is not a huge investment for a reasonable gaming PC. It also runs GMod and other similar games well. All you really need to do is locate a cheap desktop PC online or somewhere in the attic. Make sure its one with a decent processor and an AGP or PCIex16 port on it. There are plenty on eBay selling way under retail price. Once you get it, install a new graphics card. A decent one only costs <30$, because the technology for the old systems was cheaper (assuming its AGP, which is likely).
Counter Strike: Source is a much better investment, being that it doesn't suck after overplaying for a few days straight. 1.6 can get old fast. You know you want cool physics, high def sprays, servers full of people that arent wayyyy better than you, and other stuff.
If you need help finding a new system, I may or may not be willing to assist you. :)
