Seriously? I meat the ET recommendation is spot on, that game is dope shit, but he can DEFINITELY run HL2 and CS:S with that setup. I don't know if he has a video card, but I ran it with 1.7GHZ, 1GB RAM and a shitty 128MB video card on all Medium settings when it came out. Sure it was on XP, but contrary to popular belief Vista is not a system hog. At the very least you can pull it off on low settings, without a hitch. But you can do better...
1. Go to your Start Menu and in that little Search bar thing, type "msconfig" and press Enter.
2. Hit Disable All. Maybe keep AVG if you really think you need virus protection. The rest can go.
3. Apply, Exit, Restart.
Your computer will be at least twice as fast, and then it will DEFINITELY be able to run most of the games listed here.