HDD not detected

Hi,

My OS cannot detect my seagate 500GB sata hard disk

This problem arise few days ago when my HDD works just fine until my computer faced series of freezes. I opened the case and adjust the data cable to one of my 'data' hard disk and turn the computer on and the computer works again. However, minutes later it froze with the same problem and same solution.
At this stage, my computer can read all of the two hard disks (system and data)
Therefore, i decided to send it to a repair shop.

A day later, the shop called me and told me that the data HDD could not be detected.
He said he tried:
-Switching the cables around internally
-Take the data HDD and plug it into other computers

and it wouldn't work. However, he said that something like
"the bios can still read the HDD" and "this HDD acts like a newly purchased HDD that had not been partitioned - where it will be detected to the bios but not the OS"

Anyone got ideas of the problem, or how I might recover the data?
The data inside really mean a lot to me,

Thanks you guys a lot,