Black & White 1 - A "God" game kind of RTS. (Only problem is that it's VERY hard to find these days, maybe on Amazon or eBay).Rollercoaster Tycoon 1 - The start of a great generation of theme park simulating. (Probably hard to find too).Rollercoaster Tycoon 2 - The sequel to the above, more rides and more fun. (More likely to find this, but not guaranteed to be easy).Just out of curiosity what are the specs of it besides a 600 MHz CPU?
Assault Cube.Apparently. I heard it runs on Pentium III's, but I can't confirm.
Half-Life
Midtown Madness
Also, I'm quite sure it doesn't have an Intel graphics chipset, unless you looked in Dxdiag. Most computers from these days had stuffty ATi or Matrox cards instead.