Hard Drive Failure
Telltale Signs
Computer slows down tremendously
Boot up errors / cannot boot up
What to do
boot into safe mode and run a disk check & repair or First Aid (for Win, for Mac)
physical reseat of cables. See walkthrough with pictures here
listen for a “click” sound from hard drive
Hard drives are mechanical parts that will break eventually. When all of the above fail, it’s time for a hard drive replacement.