Just a quick note regarding Win2k, Half Life and their combination with a Via chipset. If you do run this combination, make sure to update your Windows 2000 box with the Via chipset patch (Windows Update on your Start menu should do the trick).
I as well as many others experienced problems playing over the net where you could be walking forward and then suddnely, you would be walking to side or looking another way with a different weapon selected. The Via chipset patch from MS appears to have alleviated this problem for myself and my friends.