Monitor shuts down due to new graphic card!!

I have just installed a graphic card (GeForce FX5500) and plug my monitor in the graphic card port.
However,my monitor shuts down after 1-2 mins. I use a 8SS661FXMP-RZ motherboard which have an integrated video card.
I have try to disable the video card in device manager but the problem continue to persist.
The graphic card works perfectly on my friend's computer who do not have an integrated video card.
Do i have to disable it on the motherboard itself?? I don't know how to do it!! Can anyone help me???