So to sum it all up, motherboards with PCIe is enough for games like Doom 3 right?
Most new motherboards have PCI-Express, it runs faster than an AGP bus (AGP bus speed= x4 or x8 / PCI-E bus speed= x16).
So yes PCI-E is faster then AGP but you have to take into account the 'System Requirements' for Doom 3, if you look on the back of the box of the game you want to run it will tell you the minimum system requirements needed to run the game.
A frend-a-mine bot an intel motherboard with PCIe but his NFS MW grafix sucks !! I get betta grafix wid my GeForce FX 5200 128MB.
A good graphics card alone won't make a good PC!, you cannot make a cow jump like a gazelle
Basically, imho, the more RAM (preferably DDR400) the better, 1Gb DDR400 is good, also a good, fast CPU does not do any harm.
for more information for Doom3, Quake3 etc. You will find the compatable hardware list there too.
What version of Direct-X do you have?, Doom3 supports/requires v9.0(c) to run at it's best. Maybe you're friend did not have the latest video drivers?, currently 81.98_forceware
<-- click here to d/l 81.98 for XP/W2K.