The Games for Windows site has the Halo 2 PC requirements up.
They're pretty reasonable for most home PCs, but I just got a Dell 1501 laptop, and it has an AMD sempron 3500, at 1.8GHz. I have never played a PC game in my life, so I'm a n00b here. The CPU has to be 2GHz to play Halo 2, so will my laptop be able to play it? Or do I have to overclock it or whatever you call it?