PXE-E61: Media Test Failure, Check Cable....Operating System Not Found....Hard Drive DST Short Test: Not Applicable

Hi All, I own a Dell Studio 1745 running Windows 7, and have not had any issues with it for the past 4-5 years. Just yesterday morning upon power-up of my computer, the machine failed to boot into the OS, and the following error messages were shown: PXE-E61: Media Test Failure, check cable PXE-M0F: Exiting PXE ROM. Operating System Not Found. The first troubleshooting step I did was to re-boot the computer and hit F2 to enter the BIOS Setup, in order to verify the boot order was configured to display my Hard Drive as first priority - which I verified. The Hard drive was detected and was already set as first priority. I re-booted and the same error messages appeared. The second step I did was to re-boot the computer and hit F12 to run the System Diagnostics test. Everything in the diagnostic test passed, however, I noticed that the Hard Drive DST Short Test came up with a "Not Applicable" result. After the diagnostics were finished, I re-booted and the same error messages appeared. The third step I did was to physically remove the Hard Drive from the machine, and re-connect it. Again, same error messages. The fourth step I did was remove the Hard Drive from my computer and install it into a new External Case, and then connect via USB to 3 different PC's. Each PC was unable to properly install the required drivers for the external case. I could hear/feel the Hard Drive spinning inside, but the PC's could not properly install the drivers, and thus, I could not access the Hard Drive. Has anyone had a similar experience? Are there additional troubleshooting steps I should attempt? I am concerned that my Hard Drive is damaged. Please advise on how I can determine if my Hard Drive is still functioning. Any help is appreciated! Thanks!