Answer to: images appearing on screen and locking up Imac G5I had same problem with Imac 20". The video card is the problem. Found this solution on a another site. Remove this extension: ATIRadeonX1000.kext. It is located at: system/library/extensions. You can start up in safe mode, then go to the extensions remove it (I saved a back up of it on an external drive just in case). You're Imac will work but the only thing I've heard is that graphics that use quartz will not display. I haven't found many things that don't work and since I use it for internet and some work it is all good.