I have an Alienware M7700 laptop. It about 18 months old now. Other than the fact that it runs thermonuclear, I love the thing, It plays all my games pretty well in fact. It's great for LAN parties and such.
I have never had problems with my games except once and that was due to a bunch of junk that came in while I was attached to a hotel network.
Long story short, mine works great for gaming.
Make sure you don't have the normal junk like a virus, or spyware.
I cleaned out the vents that allow hot air to flow out and I recommended the owner of the Alienware to use a cooling pad. Apparently he was using it close to a wall where the GPU vent could not breathe. It's been running fine now with the cooling pad and the vent not closed in. The thing has the 7800 Geforce and a 3.8ghz P4 HT. That thing can heat a house in the winter!
The HDD light is always on in C&C Generals now but it doesn't affect gaming performance. Screw it.