Three monitors, ATI onboard and Nvidia PCI

I have this computer that I bought as a barebones kit from TigerDirect.
-Gigabyte motherboard
-AMD processor
-Onboard ATI Radeon HD 4200
-currently only 3gb RAM
-Windows XP media center edition
Then I installed an Nvidia Geforce 9500 gt GPU (1gb)
Next I proceeded to stick a second monitor on it (both are 19 inch, 1280x1024 res)

The problem is first person shooters suck at two screens due to the crosshairs being in the middle.
So what did I do? Pinched a monitor from my dad's computer room and stuck that on my onboard video card, that Radeon.

Now my problem is (since I used nvidia control panel to manage the two monitors on the 9500, and catalyst control center to manage the third monitor on the hd4200) I seem to be unable to make the desktop SPAN all three monitors instead of "dual view" stuff that windows does.
I can arrange them properly and stuff and set pretty wallpapers with DisplayFusion, but i still cannot play games that span the entire three-monitor desktop.

I'll be anxious for any help you guys can offer
Thanks,
-Nick

you need a amd card with eyefinity is you want to do that, tell me what cpu and power supply do you have, and your budget

what games are you planning on playing?

for the third monitor i would recommend an hd 6670 or hd 6790 at least

you can put any of those gpus on the motherboard, i believe you'll need to get a display port to vga adapter

that card is too old for that technology, you need at least a 200 series card i believe, get a cheap 6670 if you want to spend as little as possible, you'll be able to run your 3 monitors