How to disable on-board graphics card?

Hi There,

I have a 2 yr old Dell Dimension Desktop with Inter P4 (Not sure what is the
model of Mother Board). This mother board consists of on-board (Integrated)
Intel(R) 82845G/GL/GE/PE/GV Graphics Controller.

Yesterday, I purchased a Norwood Radeon 9250 PCI graphics card and I
installed it.

After installation of new card, the following has occurred:

• When my monitor is connected to PCI Radeon card, I am able to see initial
boot up screens (till I select what OS to boot).

• But I need to disconnect my monitor and connect it to Integrated Intel
card to view the rest of the screens.

I tried to disable my Intel card thru BIOS, but there is no such option. Did
anyone got the same problem?

Can anyone suggest me how to disable my On-Board Intel Graphics Card?

Thanks in Advance
Kode.