SMART Hard Disk Error

[Hunkutensewanu]

This is the message prompt I keep getting for some time now: 

Smart Hard Disk Error

The Smart hard disk check has detected an imminent failure. to ensure not data loss, please backup the content immediately and run the hard disk test in  System Diagnostics

Hard disk 1 (301)

F2 system diagnostics

enter - continue startup

for more information, please visit www.hp.com/go/techcenter/startup

Furthermore ,

I clicked F2 

the Memory test - passed

But HARD DRIVE CHECK says- NO Hard drive installed. please check that the power and data are connected properly

I have removed the hard drive and re-insert again but yet no improvement

and when i exit the f2 command dialog page, here is what i got

Boot device not found

please install an operating system on your hard disk....

please how can i rectify this problem as i will not want to loss vital data stored on the hard disk..

kindly note that i removed the  Hard drive and fixed it into a hard drive case so as to connect directly to another pc.. the hard disk was rolling but it didnt connect to the pc

i need your help urgently