1. The graphics driver needs to be reinstalled or updated.. Visit the manufacturer's website to download the newest video driver, then install it..
2. If that doesn't help, then the display screen is going south.. It could be a cable or the actual screen failing.. Either way, most home users will need to take it to a repair shop.
Hope this helps.
My Pavillion dv9000 entertainment laptop works perfect one minute then will suddenly show colored lines all over the screen, sometimes circles, spots, all over different colored "snow". It then is unresponsive and I have to force it off. It turns on in safe mode sometimes visually perfect, other times with transparent blue squares that will change when the mouse travels on the screen. Then I restart and it will work fine for sometimes an hour and do it again. I ran spyware and maleware programs but nothing showed up on that.