24" Imac Display trouble. HELP

[Gamey]

Suddenly and w/o warning my 24" Imac has started to show squiggly lines all over the screen. I have tried re-booting but it just seems to get worse when I do this.
Here's a screenshot of my desktop to show you what I mean.

Any ideas before I get on the phone to Apple

 

[Benjamindaines]

That's a problem with your graphics card, take it to Apple for a repair. Make sure you backup your hard drive, you will probably get it back with a fresh install.