Onboard Graphics Card Locked

So, I bought this used Dell Optiplex 755 SFF, and it has a Radeon HD 2400XT installed, but I don't have a DMS-59 cable so while I wait for it, I wanted to just plug it in to the onboard graphics accelerator. I tried doing that, but the computer just booted up and gave me this message: Onboard Graphics Disabled. Please plug in to graphics card.

Some message of that nature in description. Anyways, how the heck do you disable/lock the onboard graphics accelerator on the motherboard? I didn't even know that was possible. I really want to turn on the desktop to see how it runs but I can't because I can't use the VGA cable, because the integrated graphics card is locked/disabled.

Any help please?

Thanks!

Ok what is happening is that you have a GPU installed, as well as integrated GPU. When you have a GPU PCIe graphics card installed, your BIOS automatically disables the ONBOARD video card.

What you can do as a temporary fix is - open up your computer (of course make sure it's shut down, and unplugged from the wall), take out your graphics card, and now take out the little watch battery (CMOS battery) for a good 5 minutes. Press the power button a few times while the CMOS battery is out.

Once done, leave the graphics card out, put the CMOS battery back in, and now try using the onboard video output again. That should allow you to at least get it going.

Thanks guys. Going to try both now. I don't think I can get into the BIOS though because before the computer even has time to load anything it goes straight to that message.