Why am I getting lines across the screen of my iMac?

Episode 957 (1:46:01)

Christian from Irvine, CA
Apple iMac

Leo says it sounds like a hardware error. First, he should boot from the software disc and see if it happens. If it doesn't happen there, then it's a software error. If it still shows up that way, it's a hardware error and he'll need to have it repaired. The Chatroom agrees that it's likely a bad monitor or the video card subsystem on the logic board. That'll be almost as costly to repair as getting a new iMac.