There's a significant difference between Doom 2 and Doom 3. Doom 2 still used JPEGs for the monsters. Doom 3 requires significantly more processing and graphic power. A Doom 3 'lite' would be exactly the same as Doom 1. In case you guys didn't know, Doom 3 is a remake/retelling of Doom 1, but in 3D. So Doom 3 lite is Doom 1. Doom 3 is 'Doom 1 heavy'. If you want to play Doom 3, get a better computer. Or the best option is to buy an xbox for £70. It's cheap and it runs Doom 3 like a dream.