If it only does it in Regular Boot, then it could be some hardware problem like Video card, (Quartz is turned off in Safe Mode), or Airport, or some USB or Firewire device, or 3rd party add-on, Check System Preferences>Accounts (Users & Groups in later OSX versions)>Login Items window to see if it or something relevant is listed. Safe boot may stay on the gray radian for a long time, let it go, it's trying to repair the Hard Drive One way to test is to Safe Boot from the HD, (holding Shift key down at bootup), run Disk Utility in Applications>Utilities, then highlight your drive, click on Repair Permissions, Test for problem in Safe Mode. I already tried all from the following listīootup holding CMD+r, or the Option/alt key to boot from the Restore partition & use Disk Utility from there to Repair the Disk, then Repair Permissions. Just take off the base, remove the metal mesh Airport antenna, and then pop out one drive and mount the other.

Also doesn't require taking the whole freakin' computer apart. Less internal storage that way but just as fast for booting and whatnot. You can also just take out the hard drive (put it in an enclosure) and put in an SSD. OS X may have the hard drive kind of busy the first few days you use it - it'll figure out what needs to be on the SSD and what should be on the hard drive automatically. Reinstall Mavericks from USB, restore the Time Machine backup, and you're right where you left off only this time with much better performance. Beware this wipes everything so that's why Time Machine is important. The fusion drive setup was really easy - fire up Disk Utility and it shows the two drives in red and just makes the fusion drive for you. I created a USB installer for Mavericks, made sure Time Machine was up to date, then installed the SSD in the top drive bay (that was the hard part). That's with basically the same hardware as you. Now I have a 1.25TB Fusion Drive and boot time is about 10 seconds.

I ended up getting the dual drive kit from OWC and added a solid state drive in my Mini. These things are slow as heck to boot up and at least in my case, the fault laid with the hard drive.

Mac mini late 2012 i7 16gb ram