not getting a image when i start my computer ( only the boot screen) after...

[raven]

...that all is blank? when i turn on my computer the screen goes blank after the boot screen is displayed (which shows up fine) but, the log on screen and everything else is blank. i can enter my password and windows starts and everything is running fine but, the blank screen. i have the on-board nividia GeForce 6150 LE no other graphics card. this happened like other problems I've had one day everything works fine i shutdown my computer and the next time i go to use it "ta da" . one last bit of info a few hours before i turned my computer off i tried installing age of mythology but it said my graphics card was not supported so i uninstalled it still no problems and everything was working fine . but like i mentioned earlier i turned the machine off and when i went to get back the next night nothing but the boot-screen displays everything else goes blank....... any and all advice is most welcomed and greatly appreciated. thank you all