My computer has a partitioned hard drive and has both windows 8 and windows 7. I have only used windows 7. When I turn it on sometimes it will load all the way to my windows 7 desktop then it says the display graphics quit working and then goes black but the screen is still light up. I have a NVIDIA graphics card. Can someone help me figure out what the problem is and help me fix it.
Welcome to sevenforums.
Fill in all your system specs in your profile, the best that you can.
That sounds like a video card not getting enough power, (or is broken) like if you booted up and forgot to connect a 6pin power connector or PSU could be too weak (broken?) to handle the card.
Or a heat issue on the video card itself, like thermal paste and/or heatsink fan failure.
The monitor itself is still on, totally from it's own power.
I would acquire a Linux distribution LIVE disc and boot to it [makes no changes to hardware at all] and if it runs perfectly for a while, than it's not a power issue. [distrowatch.com for various flavors of Linux, get a Live that fits on CD if download size is issue]
So in summary, probably a video card failure due to lack of power issue or heat, swap the card out for an old one is first thing I would do and clean out case and check all the fans involved.
Replace paste on video card and retest if you don't have a spare old card.
Artic MX-4 is recommended thermal paste, $10 gets you multiple applications of it, I'd replace it anyway.
You able to boot into safe mode?
Quote