[«SmG» R3c0N]

Well, dude you better have a dedicated video card on your system if you really wish to play even the older games. Most games released before 2001 will work on your system. Some of the guesses that I can make are:
Quake series (upto 3).
Unreal Tournament
Doom and Doom II.
AOE series.
CS 1.6
Some NFS games (probably before Hot Pursuit 2)
Maybe GTA III : Liberty City

All of these games should run but don't expect to get around 100 fps XD
Most of them are not free.

Dunno bro, there are lots of classic games you could try, also depends on your taste.
Maybe get NES/SNES, Sega Genesis, and such emulator. Download some roms and play.