I am building myself a wonderful brand new computer and I am reusing my 1TB HDD and optical drive from my old computer to save some money but I am going to have to entirely wipe the HDD so I can use it on my new build but I was wondering if there were any important files that I should put backup and put on a USB so I can put them back on when I get my new computer going. Also how do you clear a hard drive completely so there is absolutey nothing on it?