Just for some people that thing that their PC won't run the game because it's under the minimum system requierment , well, I tested Doom 3 on a PC under the required specs (in some points) and it runs fine most of the time!
Specs:
Mobo : Aopen AX63Pro - Via Appolo133Pro+ Chipset
CPU : Intel Pentium III 666Mhz (133x5.0)
RAM : 2X 64MB SDRAM PC133 (non-ECC)
Video Card : MSI GF4MX440SE-T 64MB DDR AGP 4X - Latest Forceware XP drivers
Audio Card : Creative Sound Blaster Live! 5.1 Digital (SB0220)
HD: Seagate 4.3GB HD (Doom3 takes only 1.5GB)
OS : Windows XP Pro (no SP1)
Doom 3 settings:
-Low details
-640x480
-everything at off in the advanced video options
Game takes a while to load (still average, take some mins, ingame, when game is fully loaded, the FPS goes from 8 to 20 at some places, it might drop a bit in big rooms with many special effects but it's mostly playable and the PC doesn't overheat
If you still don't want to buy the game because you are still not sure, don't buy it, it might work great for me but not for others......