Hard disk problem

[danteoo7]

i have 2 hard disk 250 gb seagate and the problem is with 500gb seagate hard disk the problem is
when i start the computer bios show both hard disk but my pc always hang at welcome logo so i restart my pc and the bios only detect my 250gb hardisk and if i completely turned it off then bios can again detect both hard disk but again same problem

note:- when bios doesn't detect my 500gb hard disk i can still see that its processing or vibrating
one of my friend suggest me that it is the problem with pcb of the hard disk

please help me my data is very precious for me

 

[danteoo7]

but my pc doesn't start with the faulty hard disk