Trying to figure out what happened to my wifes computer. Here is the situation:
She was working on her Mac Pro today when half the screen went black and the other half began to flicker. It didn't freeze up though so she shut down and tried to reboot. Instead of rebooting though, she gets as far as the apple logo screen at which point the entire screen goes pixely and the system freezes.
My first thought was hard drive. She called apple and they said it also sounded like a hard drive. So she grabbed her hard drive and went to the local apple store where they confirmed that her hdd was in ugly shape ( trying disc repair resulted in lots of errors and such ). Apple tried fixing the drive and managed to get it working so that they could boot from it.
Problem is - wifey just brought it home and she's back at her grey apple logo screen with missing pixels everywhere.
Any thoughts? It still sounds like a hard drive issue to me, but they seemed to have it working at the apple store. Does this sound like something else possibly?
I"m going to try and reformat her drive by zero'ing it and reinstalling snow leopard. Only problem I'm having now is figuring out how to open the disk drive since her cpu is frozen and there is no manual way of opening it that we can find.
She has an older G4 which doesn't include the small paperclip sized hole. Not sure if anyone has any ideas on this aspect ( opening the drive ). We've looked for a manual button with no success ... tried holding the left mouse at boot ... etc. No luck yet.
This sounds like a video card error/video cabling issue, or overheating and not at all like a HD issue. Especially your description of half the screen going black. The pixelation can be related to a variety of problems: overheating, bad card/chip, bad cable etc. . A bad HD will rarely give you the type of symptoms you are seeing. Also permissions errors are very common in the MAC OS world, so the fact that it wasn't perfect when you took it in means very little.
This may help you with your attempt at reloading the OS (but again it doesn't sound like this is the issue, especially because apple got it to boot):
To try and load your OS disk: Try booting in safe mode, holding down the shift key while booting. This will load the minimum functionality of the OS and should allow you access to the drive via the OS (if all is well there). You can also try holding down the option key on start up and using the startup manager to open the tray.
If the computer is a bit older, and has not been cleaned internally I would start there. You would be surprised how much heat can build up when dust is clogging some things up. If after cleaning the heatsink and all of the exhaust ports you still have the issue I would try what you want to do and reload the OS.
If that doesn't work depending on your technical savvy either narrow down the issue component by component or turn it in to a professional to look at.