Please feel free to skim read if haven't the time to read it all, as a complete novice, I'd really appreciate your help. My screen started to flicker with colours and black blocks, it seemed to recover after a while, but flickered again and froze completely leaving background noise still playing, the mouse still movable, but the keyboard unresponsive (e.g. volume up/down). Now when I try to boot up, there's a chime, the grey screen, then the loading ticker appears, but freezes after a while. There's also some patterns that appear on the grey screen and when using alternative methods of booting up: - I tried Recovery Mode, but it freezes, so then I can't try Disk Utility or an OS re-install - Safe boot (+Verbose Mode) will also freeze (see results in images) - In Single User Mode, FSCK -FY eventually said 'volume appears to be OK' - An NVRAM reset just resulted in a louder chime when booting up For some reason my S/N (VM84539P0KM) didn't match the ones on the Apple website, but i believe to be a 24'' 2007 or 2008 Aluminium model that definitely shipped with OS X 10.5. I was running the latest version of Mavericks and installed the iTunes 11.4(?) update for the upcoming iOS 8 when the issue occurred. I hope you can advise me if it's as easy as taking off the glass screen, unplug old graphics card and plug in new one, as that's as far as my DIY skills go (if it is the Graphics Card) and ow much it's likely to cost if I go through Apple to repair it. I'm based in England and at the moment I'm quite far from an Apple Store and any Authorised Repairers so I'm yet to contact them to see if they have some kind of Collection service.