Heres my spec:
AMD Phenon II 940 @ 3.5GHz
4 Gb ram
2x msi hawk talon 460GTx cards
Windows 7 x64
Now I have formatted and reinstalled windows, reinstalled fallout 3 and copied over a working back-up of my old game folder like I have done before without issue and the game is running perfect (albeit @ 30fps) with all my mods ect working as they were before, all settings are maxed out but it I no way maxes my system with only about 25% load on my CPU and less than 40% on each of the GPUs but again the GPUs are not running @ full 3d clock speeds these cards have 3 power levels 2d, basic 3d and full 3d, fallout is running on the basic 3d mode
Other games run fine crysis 2 maxed out and getting 60fps ect so no problems with the system or drivers, anyway I hope someone knows what's going on with this there are so many new mods around now and with fallout new Vegas having problems fose and patch issues I really wanted to have another play through on 3