Pink and green lines all over screen, does anyone know what it means?

It's no longer under warranty, I bought it in '07. I'll call the Apple store tomorrow, and hope it's something that can be fixed inexpensively. Can't afford a new computer now, and I need it for work. 😢

Here's another picture.

I followed your link. Held down the D key while turning it on. I tried holding it right after hitting the on button, I tried before, at the same time. Nothing happens. Just goes to a white screen with the green lines.

I just wanted to follow up on this issue. I took my iMac to the Mac clinic, not the Apple store, but this man used to work for Apple years ago, and has been working for himself fixing Apple products since. I've been to him before, and so have some of my friends, in other words, we trust him. He said it looked like it was the graphics chip, but wouldn't know for sure until he changed it, and that it could be the logic board instead. Since my iMac is 6 years old the parts are not easy to get. Apple wouldn't give him an exact price until he actually ordered the part, but was told that it would be around $350 for the graphics chip, and $400 or $450 for the logic board. With labor it would have been $90 more.

I had a couple friends ( computer geeks) look around for the graphic chip and they came up with the same price more or less. In the end, instead of putting $600 into an old computer, that would have still been running Snow Leopard, and running somewhat slow and all that, I opted for buying a new one. I did shop around for used ones, but couldn't find anything affordable, or kept finding old computers like mine. So now I'm the proud owner of a 21.5 inch ( brand new) iMac. It's smaller than my 24 inch white one, but since I've spent a month using a borrowed lap top I got used to the smaller screen. I love it! and the best part is that all I had to do was plug in my backup drive ( Time Machine) and it's just like using my old one, with all the settings, saved log ins etc.

Thanks to everyone that replied to my post! 🙂

I haven't cleaned it in a long time. I'll do that now. Then I'll run the hardware test as suggested. I can get in when using safe boot, but it still has the green/pink screen.

It won't let me run the hardware test. :(

I'm going to try doing it from the disc next.

Do I need to take it apart to clean it? Or just vac at the vents? Does anyone know how to take a 24 in white iMac apart? All the videos I see are for the aluminum ones.

Thank you! I will let you know what happens.