Remember the original Doom? If you're after some nostalgia, it's available as a free download from here. It was released by id Software in 1993 and played on the Windows 95 platform with the minimum requirements being an 80486 CPU, 50 MHz, 8 MB RAM. Doom was a ground-breaking first-person shooting game - meaning that players see the world through the eyes of the character they are playing - and it has become a classic, spawning other popular FPS games such as Quake, Unreal and Castle Wolfenstein.