System Crashing with Two Graphics Cards

[s323790r]

I recently purchased a Gateway DX4870-UB17 (running Windows 8 64-bit), and upgraded it with an AMD Radeon HD 6450 (active through the PCIe x16), as well as a smaller nVidia GeForce 8400GS (active through PCIe 1.0). I had finally gotten both cards running simultaneously to enable a 3 monitor system with the following setup:

Integrated Intel HD Graphics (HDMI & VGA):
Disabled, with no way to enable while other graphics cards are in ports/installed.

AMD Radeon HD 6450 (HDMI, VGA, DVI):
Enabled on PCIe x16, running two identical monitors, one on HDMI and one on DVI. No way to enable the 3rd output port while other two are in use (no matter what the configuration is).

nVidia GeForce 8400GS (VGA, S-Video):
Enabled on PCIe 1.0, running an RCA LCD at 1920x1080 as a 3rd monitor.

After installing the correct drivers for each, I can get the monitors running and working adequately. However, after an indeterminate amount of time, the LCD running off the nVidia card will lose signal, then after a minute the cursor on the screen of the other two monitors will freeze, and the computer will restart itself, and note that it has "recovered from an error."

Any idea what might be causing this? Is it an overload on power, causing the machine to reboot? Is it lack of memory?

Also, is there any way to have the integrated Intel HD graphics enabled along with the other two cards installed? I can't seem to run the Intel graphics set with anything graphics-related installed. I also can only get to the BIOS by removing both cards. If either card is installed, no signal is received by the monitors until the Windows "Starting..." screen pops up.

Thank you in advance!

 

[maxinexus]

You should have bought this
http://www.newegg.com/Product/Product.aspx?Item=N82E16814131481

you plugin all 3 monitors into this card and you should have no issues.

The problem is that you are running 2 different video drivers at the same time.

 

[s323790r]

Wouldn't the conflict not allow them to run simultaneously at all, not just work for between 2-12hours then shutting down? Sometimes at full use, it will work well for 12hrs or more, then reboot.

 

[bobvania]

The AMD HD6450 should be able to run 3 monitors with eyefinity by itself. You should not need an additional card especially with two different drivers.
You have the three inputs, you may need an adapter to use all three at the same time.

 

[reaper2k1]

hey, I have the same pc and im running into a problem the slots on back of pc where card peaks out, theres only one slot that's open, the other 3-4 are closed and I cant get them out, do icut them out and make room for the gfx card?