Recently one of my PCs ran into a problem. When I switch on the CPU, the LEDs glow, the fans (the processor fan & the PSU fan, both) function well & the keyboard & mouse receive power from the CPU. But, there's no display even if I wait for long. I took the pc to a local computer repair shop. The person at the repair shop removed my hdd, put it on a hdd case & checked the health of the hdd in his laptop. He showed that my hdd has low health (2%), I looked at the laptop, the software (I don't know what the software was) displayed that the hdd has only 2% health. The person said that I should buy change my HDD, then the CPU would be alright. My questions: what was the software that the person used to check the status of HDDs? What does it mean if the hdd's health is low? What could be the reasons for the low health of hdd? Health of HDD can be increased by using softwares or by running commands like chkdsk, sfc scan?