Hard Disc not Installed

I have a problem with the hard disc on my laptop. The laptop dies randomly during my work. I have been asking for along time to detect what is the problem and yet no result. My laptop is inspiron 15 3000 series with a 1 TB hard disc drive. I have been using it for approximately 2 year for some programming and other normal work. I have 220 GB of media videos that I transferred from external hard disc. In this particular I went to a local fixing centre and the guy who worked there told me that my hard disc efficiency is very low( approximately 9%) and that was because of some virouses in it. So I have these questions: 1- Can a 1 TB HDD hard disc be damaged from virouses so its efficiency is that low(9%)? 2- Can I just format it and then it works properly? or I just have to replace it with another one? (taking point that I once (or twice may be) opened the laptop from inside and made sure there is no problem with the cable or the hard disc it self)