*Freelancer will run on just about anything. I have it running on my netbook.
*Unreal Tournament 2004 on lowish settings should run fine.
*Lots of options with strategy games. I wouldn't recommend Starcraft 2, Command & Conquer 3 or Supreme Commander. But you might be able to get away with running C&C Generals, Sins of a Solar Empire and older classics like Starcraft, Red Alert 2 and Age of Empires 1 and 2.
*Mechwarrior 4 Mercenaries is completely free now and easy on the hardware.
*Diablo 2 and Torchlight should both run fine on your hardware.
*The original Halflife and it's expansions are still worth playing through. Get Team Fortress Classic and Counter Strike and install some bots.

Unreal Tournament
Diablo 1 & 2
Thief 2

Those are what I used to play in the day. You could also try Divine Divinity or Age of Wonders. Divine Divinity is kind of like Diablo with more role-playing, though I haven't gotten far in it. Age of Wonders is a strategy game with wizards that can be very addictive.

I have yet to find a TBS game that has surpassed the AOW series. It's well past due for a sequel.

Not at all... My netbook is about 45% faster than your setup and Minecraft absolutely murders it.

Some have mentioned Starcraft 2...I wouldn't try that either. It played well with 4 drones on the screen on the lowest setting but after that it was a slaughterfest.

Neverwinter Nights Diamond Edition, a game like Civilization (one of the older ones) will take a lot of time. Rise of Nations is good or Rome total War can run on pretty crappy laptops.

You should try the new Advanced OpenGl option for Minecraft. I tried it on my old computer a few days ago and the game ran a lot smoother.

Civilization or Pirates!

Sid Meier's games will eat up your time like fat kid and cake.