Try downloading a boot disk like the Windows 7 repair disk or even a Linux distro, now put that on CD or USB and boot into either of them, see if the HDD appears now mate.
If it dont then either undo the back [panel and take the drive out and mount that in a caddy or just pull it out and out it back in again.
To boot from a bootable disc you will need to change the boot order in the BIOS so that the optical driver is the first device in the order and the hdd is the second device.
Let's kill two birds with on stone. Down load SeaToolf for DOS, create a bootable disc from the ISO image and run the diagnostic tool.
Notice: This applies only to Windows 7 and Windows 8, earlier versions do not have this.
1. Place a blank CD or DVD in the tray of your optical drive and close the tray.
2. After you have downloaded the ISO image you want to burn right click on the Start orb, then choose Windows Explorer.
3. When Explorer opens click on Downloads in the left pane. Scroll down till you find the ISO file you want and double click on it. Click on Burn Disk Image.
4. In the image below you will see Disk burner:, this should be set to the optical drive you want to use. Click on Verify disc after burning if you want to Windows to verity the disc image after burn. Click on burn.
5. In the image below you can see that the green progress bar, when the image is finished burning the bar will be filled.
6. After the image has completed being burned click on Close.
Once the disc is created load it in the CD/DVD drive and restart the computer.
If the disc is recognized you should receive a message instructing you to press any key to continue to boot from the disc.
Please note: You may need to change the boot order in the BIOS so the CD/DVD-ROM is the first device in the boot order, and the hdd is the second device.
Please run the short test and include the results in your next post in this topic.