It sounds as if your graphic card settings have altered. Right click on your desktop, then on properties from the drop down menu. then on the settings tab. see if you can move the slider over to the right. choose 1024x768 for a 15" Laptop display and your colour should be at a setting of 24bit or high colour.
This should solve the problem, if not then click on the advanced button, "Lower right of the same window" click on the adaptor tab, then properties again, then the driver tab. Click on "update driver" and windows will search for your driver details and update them.
If this does not help, please post back for further advice. j.