Question PC wont boot if i connect my harddrive.

[middleclassuser]

My system wont boot if i connect my harddrive. Its a SEAGATE SKYHAWK 1tb HDD.

Let me explain the whole scenerio.
i was working in my pc and suddenly a pop up message came internal hardware error or something.. suddenly i was not able to access my HDD. i just rebooted the pc and its not booting.. My boot drive is a separate 240gb ssd. so i removed my harddrive and turned on the pc, then it worked.. so i connected my harddrive back again and then slowly the system booted suddenly i checked the SMART status. it said good 75% health. So i thought it might be any sudden fault. i restarted the pc for crosscheck, and then pc stuck at bios screen. Hell!!. i removed and reconnected harddrive and booted fine. but if i restart it wont boot so i just kept the drive for backing up data.. i started the backup process and when i copy anything, it starts normally and at the middle it gets stucks and says internal hardware error and hdd disconnects... after this happening 2-3 times the harddrive stopped detecting. The motherboard will get hanged at bios screen. System isnt booting... So i tried to check wheather there is un usual clicking or cracking sound inside hdd.. when the hdd powers up there is a cling sound just as normal and after that only motor spinning sound so verified the disks are normally spinning.. so i just unscrewed the pcb board and found that the data points and the points which connect to the motor are dirty it was colored dark.. i just clened it to shiny and reconnected the hdd to pc.. still same problem.... someone plzzzz plzzz help me to get my data in the harddrive

 

[Nine Layer Nige]

When an HDD starts to fail, thats it, get a new one.
If you only use it as a backup drive, get an SSD to backup onto as the backup time will be much faster.
If you need to get data off of the failing disk, then you might be able to boot up with the failing HDD sata cable disconnected, then when booted try connecting the sata cable and see if it is detected, but you may need hotswap ON selected in the BIOS.
Alternatively, use a USB3 adapter to connect the HDD to the computer and try to get the data copied over to another disk.

DO NOT RELY ON YOUR FAILING HDD !!