Hello there. I have a mid 2011 MacMini that I am having issues booting. Once it powers up it will display the apple logo and while the loading bar fills, when it reaches about 1/4th of the way a clicking noise is heard and the machine reboots. It does this a few times (about 3) and then it powers off. It has one monitor connected to it, a wireless Logitech keyboard and mouse and a couple of external HDD attached via USB. This issue started a few months ago, but would not happen always, then it got more frequent until one day it started doing this. I just downloaded and reinstalled Yosemite, but didn't erase the Bootcamp partition, but did erase the Mac side. During the installation it seemed that the machine rebooted once or twice without issues, but then it got stuck again. I have previously replaced the HDD with a Samsung 840Evo drive, and the issue is the same. When I replaced it with the Samsung drive I didn't have issues for a few days then it started again. I have installed an older OS version and seemed to have less issues booting up but then it happened again, right after upgrading to Yosemite. Though the first time that I installed Yosemite I had it running for about two to three months without any issues. I have tried removing the external drives and just booting the machine only with the monitor and the issue continues. When I go in repair mode and an issue with the HDD gets reported and when I try to repair the Disk Utility isn't able to. This has happened with all the drives so far. I am recovering an old back up now and was wandering if anyone had encountered such an issue. I don't really want to send the machine in to a store to get it repaired, so I am open to any ideas from you all. Thank you, Endri.