Hey, we're here to help. Take a few deep breaths and realize that it isn't the end of the world.
From what it sounds like, you're having an issue with your graphics card. Try updating your drivers (go to Nvidia.com and select Download Drivers from the top menu navigation bar. Click the options corresponding to your video card and operating system, and the wizard should walk you through it.)
After you install the drivers, restart your computer and try again.
Alternately, if that doesn't work, you might not have enough Video RAM (V-RAM, or video memory). Check to see if your card meets the minimum required or recommended specifications that the game asks for. If it doesn't, you may need to upgrade your video card (should be less than $100, you can get a good new or used card for about $50).
Again, it's not the end of the world, but it sure is annoying. E-mail me if you need any further help, and I'll be glad to walk you through any and all steps.
Good luck.
EDIT: You can also check to see if your computer needs any patches by using Internet Explorer to go to http://update.microsoft.com and following the prompts. Choose "express install" and the software will look for any patches you may need.