Windows 7 My laptop cannot find my graphics card.. causing BSOD?

[champak256]

My laptop (Samsung RF411) has the Nvidia 525M graphics card, but for a few days, my laptop has been unable to recognize this fact.
sometimes, after my laptop turns on, Nvidia control panel launches, and I can use it, change settings, and use the graphics card, but sometimes Nvidia doesn't launch, and I am not able to launch it, as it says, "An NVIDIA graphics card was not detected on your system."

This has started after I had to get my motherboard replaced by samsung because suddenly my laptop would not turn on. The original problem is fixed, but now my graphics card seems to be having problems.

The Intel integrated graphics is still working, AFAIK.

I suspect this is also the reason behind my recent BSOD.

HELP!!!Link Removed

 

[champak256]

I should add, I only noticed this problem after trying to run Halo Combat Evolved on the laptop. It got stuck after the sponsor animations, and I could hear the Menu music and sounds, but could not see it. When I quit, I took a stab at fixing the problem and noticed the graphics card was not detected.

I just restarted my laptop, and NVIDIA is working again... for how long, though?