Hi, I'm new here so hope I've posted this in the right place! I'm on a desktop Mac from late 2012 running Yosemite (10.10.5) and it's been running absolutely fine for months until this last week when I've suddenly been experiencing extremely slow boot up times. This morning, it took almost half an hour to boot-up! I have no idea why this has happened because although the machine is a few years old, the specs are still decent and there's no way I should be waiting that long for it boot up when previously it would take less than a minute. I get to the screen with the grey background and the dark grey Apple logo with the loading bar underneath, and that's when I end up waiting for what seems like forever. Does anybody have any idea what might be causing this, and how I would go about diagnosing/fixing the problem? The specs are as follows: OS X Yosemite 10.10.5 3.2Ghz Intel Core i5 16GB 1600Mhz DDR3 RAM (2x 4GB sticks and 1x 8GB stick) NVIDIA GeForce GTX 675MX w/ 1024MB RAM 1TB SATA HDD (758GB free) Thanks in advance!