I decided to upgrade to Mavericks and now I have a huge brick on my desk. Specs: I have a MacPro 3,1 dual quad core 2.8GHz, running 16GB ram. Two graphics cards one supported and one not so much. ATI Radeon HD 2600XT 256MB and a Gigabit brand GeForce GTX 650ti w/2GB Ram running two Samsung S27B350 HD monitors. So ... I wanted to check that the hard drive was without errors before upgrading. Unfortunately there were errors, booting into the recovery HD to repair the hard drive failed. I was given a message that the hard drive could not be repaired by disk utility. Thus starts the major downward spiral of my Mac. I decided to do a clean install after reformatting the hard drive, so I created a bootable USB of Mavericks, booted up into the USB, used disk utility to erase and format the system drive for a clean install. The install of Mavericks locked up 4 minutes into the "preparing files for install" so I made another attempt doing the same steps, boot into the USB, erase system drive, install Mavericks. This time it looked up at the 5 minute mark. I waited for over an hour to see if it would resolve, still nothing. Did a hard shut down to see about preparing a new boot drive. All this while fighting the displays, I left the radeon card in place just for such an occasion. You see, the GeForce card does not display during the boot sequence. However, the Mac kept getting confused with the displays. The radeon card even with only one display plugged in would display the apple logo on the primary display, but switched the login, drive select etc screen onto the invisible (not plugged in monitor) so there was always a search to find which outlet on the card was passing the display. At one time it even showed up on one side of the GeForce card. Soooo ... Here I am, unable to get even a " no operating system" warning to display. I have verified that the boot drives (three different ones, one has Lion loaded onto it) work when I boot them up on my MacBookPro, however there's a working OS on that machine. Sorry so long ... My question ... Since the OS was whiped out, am I dealing with a graphic card that can't display for lack of drivers, or could the card have suffered an untimely death. I can't rely on the GeForce card because it is not supported. My best guess is that the boot drives are working I just can't see them. Both monitors are working too. I tested them with the MBP. Or ... Is this an issues because there's not a working OS on the hard drive anymore? Any suggestions would be greatly appreciated, thanks!