It only took me a year to figure it out, but I've confirmed that the problems I've been having for the past year with the screen freezing (thought the computer was freezing) are owed to a bad graphics card. The card I have in my 2.16GHz 24" iMac (purchased Sep '06), NVIDIA GeForce 7300 GT, is indeed ready to die. I found some articles that said the graphics card is easily upgradable in my iMac. If true, which replacement card should I buy? And is this something I can install myself, simply by removing the cover, pulling out the old card and installing the new? Thanks in advance!