Do it in the Device manager.

There is no provision in the D2400 bios to disable the onboard video.  The bios is designed to detect the presence of a PCI video card and make use of it.  The only choices you have in setup are "Onboard", which forces the use of the integrated video, and "Automatic", which allows the bios to use an added video card.

 

I was affraid of that.  I'm trying to add an ATI Radeon 9000 dual-head video card, and a Philips 713X TV Tuner Video Capture Card.  I can get the Radeon card to work, and even display video on both the two Radeon outputs and the internal adapter, for a total of three monitors with video.  However, the 713X TV card will not work properly.  It can capture video from the video in jack, but the TV tuner will not work.  I can't even get it to stay on cable.  If I select cable, it goes right back to antenna.  I put the card in without the Radeon 9000 card, and the TV card works fine.