iMac crashed, has a weird screen when I try to boot (which it doesn't). What's wrong

[daanw]

My iMac 24" (model late 2008, I think I ran Lion or Mountain Lion) froze when I was working in Adobe Photoshop, so I had to manually (using the power button) turn it off and on again. Then, 5 minutes later, working in Photoshop again, the computer froze again. But when I manually turned it off and then tried to turn it on again, it wouldn't boot. The bootup screen freezes when the Apple logo is on the screen and the loading icon appears underneath that. Also, the display acts all weird, which is kind of troubling:

Close up:

Then I tried different keyboard combinations for booting. When I tried cmd + shift ("Safe Mode" or "Safe Boot" I think it's called in English) a loading bar appeared and it loaded all the way until complete. Just when my hopes were up, the loading icon above appeared and it froze again, only then with a different loony pattern:

Does anyone here know what's wrong with my iMac? And what I can do to fix it? FYI: I don't have Apple Care.

Thanks!

iMac, Mac OS X (10.7)

 

[RageDaddy]

GPU is busted.

https://discussions.apple.com/thread/5002466

 

[PannaKO]

I would agree.

My Graphics Card went bad in very similar circumstances and have virtually the same visual problems as you have...

https://forums.macrumors.com/threads/1777005/

 

[ryguy92000]

Unfortunately the only thing this could be is a failed GPU. Some units have a replaceable graphics card, and I am uncertain if it is your model. If it is not the only thing is perhaps to find a place will to buy it for parts if you don't want to do a complete logic board rebuild which is not usually cost effective.

Good Luck!