If AHT confirms a hardware error, does this mean that without a doubt (100%) that there is a hardware issue? The reason I ask; I live a long way (one day travel) from an Apple Service Centre and I have already had 3/4 repairs completed for an ongoing problem caused by a replacement hard drive programme (hard drive replacement, 2x new power supplies and a new logic board). Apple wish me to travel to the service centre again to confirm another hardware issue before they can approve a replacement machine but I am currently unable to waste another two days travel (there and back) to drop off my iMac and another 2 days travel to collect my iMac, 4 days travel and 2 hotel rooms in total. I have now been without a working computer for over 2 months and Apple engineers are taking forever to confirm this is a hardware issue in order to approve a replacement. I have also been working with them to try and reinstall the OSX via recovery mode but the HD will not format in disk utility or via terminal, errors appear or the commands stall. So, is there any way that this could be a software error?