One day when I can home I turned on my computer.It was stuck on the loading operating screen for awhile and I did not know why. After a few seconds it said Disk boot error press ctrl, Alt, Del to restart.I pressed those three keys and nothing happened.So I physically pressed the restart button on my pc case.Said the same thing.So I shut downed my computer and it finally worked.The only time I saw this happen when I was trying to switch out my old HDD for my new SSHD hard drive and that was like 5 or 6 months ago.I am really worried and I am running on windows 8.1 and have NO idea why this happened.This happened on my custom pc.I scanned for viruses and nothing showed up.I am worried that this might happen again.Any ideas on what it could have been?Any ways I can prevent this happening again?