Hard Drive not working.

So the other day my computer fell over and got unplugged. When I turned it back on it wouldn't load windows. I checked connections and everything. The diagnostics said that a hard drive was in fact there. I figured maybe it was the computer so I put my laptop hard drive in. Everything went well and started up normally. So it must be the hard drive. When I start up I can hear the hard drive running so idk what is going on. I tried safe mode and startup repair an crap with windows 7 but it wouldn't work. So I ordered a hard drive enclosure. I put my hard drive in while using my other hard drive my computer recognized that there was a device being plugged in. It loaded a few drives. One titled SYSTEM one titled HP_TOOLS one titled HP_RECOVERY and one titled local disk. It won't let me open local disk. Every time I try it crashes windows explorer. I then tried booting windows from USB. Wouldn't load windows from then either. Can someone, anyone tell me what is wrong with the hard drive? How can I fix this? I'm on win7 x64. Please someone help I am in dire need of my hard drive. I only have some of it backed up and I need all of it.