Laptop screen problem

Dell Inspiron 9400 with nvidia Geforce Go 7900 GS display adaptor.

Screen shows lots of little green wavy lines in the background also when (for example) games is clicked the new window opens with large white and blue sharp angled shapes in the background. When I return to desktop the sharp angled shapes remain on desktop and most of the desktop is covered with these shapes. I presumed the above adaptor was not working correctly but when checked the message reads "this device is working properly".

I hope I have given a good description of the problem. It was a little hard to describe.

Many thanks for any help.

 

Ok new info re my original problem. After I posted to the forum the computer froze and the following message appeared on my screen " the driver nvlddmkm stopped working and successfully recovered", then the screen went black and the computer closed down. When I restarted the the original problem was still there.

Help Please