Graphic card not getting activated

Hi Guys,
I have re-installed windows 7 recently.I have a NVIDIA geforce gt 540m pci-e graphic card and an integrated intel graphic card.
The nvidia drivers installed correctly.But the on-board graphics card is taking over my pci-e card and bios setting are showing my video memory as 128mb when my nvidia has a video memory of 1gb, but the device manager said that the device was working correctly.
When I try to play any game it says that the compatible video card was not detected.
Any help is appreciated. Thank you.

Hi there , just been reading about this and apparently the card uses an Optimus system that enables the computer to switc between the integrated card and the dedicated card to save power consumption, not sure if there are any settings for you to change this but maybe disabling integrated in bios could help or checking settings of the Optimus program ?