My new PC

I recently bought a brand new computer. I've been thinking about buying one for a long time. I was happy, but my brother was even happier than I was. It was like that because he was supposed to get my old computer. The only problem was that I had many important files related to my work stored on the hard drive. I needed to delete all of them from there because I already put them in my new computer. A friend of mine told me that it was quite easy to erase hard drive files. He showed me a YouTube video with instructions on how to do everything by myself.