I have a Rev. A iMac G5 20" that all of the sudden has about given up on me. After about a minute of being on the screen will go funky and then about a minute or two later it will crash and tell me I need to hold the power button down to restart. The hard drive is nearly full, but still has 3.75 GB available. Any suggestions for this deal? I'm trying to attach a couple of pictures of what the screen looks like. Thanks!