Diablo 2 is an easy game to run I played it just fine on a laptop with only 512mb of ram and no hardware acceleration and even the cheapest laptops nowadays come with 2GB of RAM.
Lots of good old games exist Biowares Infinity Engine RPG's are fun and not hardware taxing, Emulators work well, Worms Armageddon, Duke Nukem 3D, Age of empires 2 are good choices.
I suggest an Asus X50GL
http://www.dabs.com/productview.aspx?Quicklinx=5BTW&CategorySelectedId=11105&PageMode=1&NavigationKey=11105,403550000,46400000,4294953475,379190000,49350000,46140000,46460000,49340000
Not expensive £423 and has a 2Ghz Core 2 duo, 2GB ram, Downgrade to XP, Wireless, 250GB Hard drive
Now the GeForce 8200M G isn't extremly powerfull but serves its purpose if gaming is only a distraction while easily handling basic operations like Internet and any word processing while using less power and taking up less space than a conventional desktop while being usable from anywhere in the house.