External hard drive not working (help)

[PsykoSonic]

My External hard drive is not discoverable, the only way I can find it is when I go through the control panel and it tells me my hard drive is called USB to serial ATA bridge.
This happened when I ran CMD to try and restore my memory and now I've made it worse than ever. its a sonnics 500gb hard drive if that's any help.
I have other hard drives but this one is my most important one as it belongs to my work and I could get in some serious trouble for this, so any help will be extremely appreciated, thanks.