|If you booted into safe mode then the hard drive is likely OK. |
Before you do that I suggest you run a diagnostic on the exiting hard drive. Western digital have their own and Seagate and Hitachi utilities may work on any drive.
If you did NOT check the BIOS settings then the hard drive may not be in the boot order. Another possibility is that the cables are not fitting tightly.
Swapping out the hardware before diagnosing is not the way to proceed.
Run the diagnostic (drive fitness test) first and report back what you get.
message edited by OtheHill