Computer is freezing and distorting images.
My grandma gave me her old iMac 24" EMC2111 2.16ghz because it was messed up. She took it to the apple store and they said the logic board was messed up and were going to charge $800 to fix it. The computer runs fine for the most part. I try to watch a movie and when I do some times it works but most of the time it displays green, purple, or static lines flashing. Every once and a while the computer will freeze up completely to the point where I let it sit for hours on hours and it never thaws. When I first got the computer the entire desktop and every item was distorted displaying multiple images in one, static icons and everything was all together messed up. Over time I have been able to get the computer running longer and longer but it still crashes. I can not go a full day without text not displaying properly, files showing up as static, or other issues. I looked at other peoples problems with this model and I found one person who said it may be the video card. I downloaded iStat Pro to keep an eye on my core temps and I do not see my video card temps go above 40 deg C. So I'm not sure if that is it. I want to get an opinion on what it could be before i spend $250-$400 on a part that may not even be what I need.
It is displaying the symptoms of the video card going bad. Due to lead free solder and inadequate cooling in these imacs, the BGA array of solder balls connecting the video card (7300GT or 7600GT) to the logicboard fail due to whiskers and cracks. You'll need to replace it, best prices are on ebay at around $150-175. Try to get a 7600gt as these are much less prone to failure and if not get a more recent rom version of the 7300gt card.
Installation will requite torx screw drivers, and reapplying thermal paste.
In the mean time, dl smcfancontrol and raise the CPU and HDD fan speeds to help the card.
Booting into safe mode will also help.