I recently purchased a Mac Mini (mid-2010) and upgraded the hard drive to a Seagate ST1000LM014-1EJ164 1 terabyte drive. The company I purchased the machine from installed the drive and put OS X 10.7.5 (Lion) on it. I set up the machine and went in to the Application Store to upgrade to Yosemite (10.10). The file downloaded, but would not install. It gave an error message and suggested I re-download the file. I did this 2 more times to no avail. I tried to re-boot into Lion but the machine would not start up. I then built a bootable USB flash drive with the Yosemite installer. I started up the Mini off the drive and tried to start the process. It failed. I then went to Disk Utility, selected the drive (which shows as a 1 terabyte drive) and formatted it. I tried to re-install again. It failed. I'm looking at Disk Utility now and it shows 1 terabyte drive labeled as Media and as being formatted Mac OS X (Journaled). There are 2 other drives showing: disk2 that has OS X install ESD that is formatted Mac OS Extended disk3 OS X Base System that is formatted Mac OS Extended There are no indications as to the size of either of these disks, nor can I format them. My questions: 1. Do I have to use something other than Disk Utility to format the drive for OS X Yosemite? 2. Am I wasting my time trying to get Yosemite to run on the computer? It has 8 Gb of RAM with the hybrid drive. 3. Do I need to buy any other software packages to make this thing work? According to Disk Utility, the drive is listed as 1 partition that is GUID. It is shown at the top of the screen in Disk Utility, with the disk2 listed underneath as an Apple Partition Map at 5.40 Gb Mac OS Extended Journaled. The disk3 is labeled as a startup partition and that I cannot erase it. It is 1.29 Gb in size. and is Mac OS Extended. The error message when the Yosemite install fails says "An error occurred while extracting files from the package "Essentials.pkg". Quit the installer to restart your computer and try again."