"Bad Display / Graphics Problem with iMac 24" 7300GT" için yanıtI had the same artifacts problem on my iMac 24" with GeForce 7300GT onboard, Lion 10.7.5; it started like in the pic quite a week ago and got worse day by day, till the system used to hang just after rebooting. Once I could succesfully login I removed the GeForce kext (all of them) and it became usable after rebooting... but I obviously lost all the "video" capabilities, from desktop effects to movie playing as graphic acceleration had been dropped. I reinstalled SL but it could not get any far than the language selection window... it crashed every time I restarted! artifacts were also visible during installation!! So I opened my iMac! cleaned up GPU and processor from the old thermal paste and applied a new one; removed the dust off the blowers, put it back together... Tadah! It worked like a charm! after restarting the system I could go through the installation steps, then I installed a fan/temperature manager app (there are plenty of them, just google it!) and pushed CPU blower speed up to 2000 rpm......