Troubleshooting Hard Drive

So I have an older Alienware X51 with i7, 16gb RAM, and Gtx 660 and have had some minor issues since purchase in late 2013. They have consisted of random restarts, and not sure if that is relevant. Five days before I re updated to 8.1(forgot to turn auto update off). It had worked before but refreshed my pc because of the amount of unused programs installed by the family.

 The last Three of days of use it seemed fairly slow loading anything, though once they started ran amazing as per usual. The last day the disk was running at 100% most of the time, even after closing each task that was at the top of usage. I was looking for remedies to this online until bed. I had a movie running the last night of function it had and fell asleep, movie on repeat. When I awoke the screen was not fitted correctly, like a different aspect ratio or had glitched while closing. It was also frozen on a frame of the movie. I pressed power button until it shutdown. Upon restart it went through Post and loaded windows to login. I entered login info and it loaded endlessly, couple hours. I restarted it again, only this time didn't even load to login. Several more hours hoping it would load ended with it telling me the internal hard disk was not found. I entered setup from there into the bios, version A12 btw, and confirmed that it was detected. I restarted yet again, no windows, only black screen. After waiting it eventually had a white cursor then gave the same "internal hard disk not found" I ran an ePSA and it immediately told me "Msg: Hard Drive - No Hard Drive detected, or disk controller not supported" I checked it several times, several restarts same answer with all everything else testing out fine. I changed several settings, even back to defaults, in BIOS to no avail. I then, took apart and reseated the hard drive, all connections seemed tight considering limitations of the connectors and cables. No change in BIOS or ePSA. Only other route seemed to be Windows so I made a recovery media usb from newer family computer. With this eventually loading up I first tried Automatic repair, it failed. I tried to refresh, it could not detect hard drive. I tried factory reset, it could not detect hard drive. No backups or images so those options wouldn't help. I used the command prompt and ran chkdsk /R and /F on the "missing" drive C:. No errors, and it to me obviously found the drive to check it right? I then used bcdboot commands, said it found corrupted files and repaired them, they would be activated upon reboot. I rebooted and no change. No boot, and now just renamed my Internal drive Hard Disk in BIOS. No other Pc my drive will fit into to test it, and very much at a loss on what to do. Would Love any feedback and ideas. If I must replace the drive would also be very appreciative on how to get any of my files off of the Drive, lot of business files I that would hurt to lose.

Thanks, AL