I have two monitors. I cannot make doom 3 BFG use my first monitor, it always uses my second monitor. I did notice there is an option when changing the resolution to choose between monitor 1 or monitor 2. Strangely it does not matter which monitor I choose, it will always use my second monitor EVEN IF I SWITCH. In other words chaning the monitor in doom 3 BFG does not work, it always uses the second monitor. Am I doing something wrong or is this a bug in doom 3 BFG or the graphic card driver? Am I the only person that is having this problem?

This are my specs:
Windows 7 sp1 x64
Gigabyte Z68X-UD3H-B3 motherboard (Intel Z68 Chipset)
Intel core i5 2500k
16GB ram
Ati HD 4870
Latest graphic card drivers: AMD Catalyst Software Suite (legacy) version 12.6

Try swapping the monitor plugs on the video card.

And, I know you may have checked this already, but did you switch 1 and 2 in the screen where you set the offset and height differential?

CCNA, I am sorry but I do not know what you mean with "offset" and "height differential". After some more testing I noticed something even more odd. Apparently I can switch between screens by also changing the resolution. For example:
If the game is running on screen 2 with resolution 1920x1200 and I switch to screen 1 with resolution 1920x1200 then nothing happens.
If the game is running on screen 2 with resolution 1920x1200 and I switch to screen 1 with resolution 1600x1200 then the game switches to screen 1 with resolution 1600x1200. If I then change the resolution to 1920x1200 then the game runs on the first screen with 1920x1200. So if I want to switch screens I first have to also switch the resolution to make the game switch screens. It is a work around but it works. Are there other people who are experiencing the same as I am?