Windows 7: Secondary 1tb hdd missing from explorer worried to death plz hlp

Hey guys yestrdy i was using my pc as usual wid my primary 250gb+secondary1tb working perfectly fine, then suddenly d 1tb hdd drives vanished from explorer menu & in disk mngmnt it was showing unallocated.

options i tried>>
>unplugged evrythyn removed hdd connctrs n repluggd tryn diffrnt connectrs
>chkd in device manager it shows no errors
>reinstalled drivers
>chkd bios for errors but no use
then i installed search n mount(3rd party), it scanned my 1tb hdd n showd its 2 drives as unmounted, i mounted them & they were visible in explorer..only thing was dat cudn't acess all data..so tried active partition recovery..still no hlp
>>>then after about 6hrs the drives automatically became visible n workin fins again....was relieved a lot....bt d othr day it showed same problem....what shud i do to recover my data...plz help!