Screen breaking up

I have an iMac OS X 10.6.8. I think it's 6 or 7 years old. The screen breaks up every now and again where pictures become like a thread of colors, or a line runs across the screen. It has twice had a grey screen drop down from the top and sometimes it freezes and the only way to unfreeze it is to turn it off. In the last 2 days the normally square cornered windows have become curved and fuzzy and the frames are white with a yellow splash. Can anybody tell me what's going on? Is it dying? Is there something I can do?

You need to isolate the problem. Since it can either be the LCD which is dying or the graphics chipset, the best way to find out is to attach an external monitor to your iMac and see if the same symptoms are displayed.

Thank you!

I will see if I can do that. Thanks.