Use the crack it’s easy and free. I’ve never paid for Microsoft anything. They are an evil monopoly. Openoffice and libreoffice take some getting used to so I never learned them.
The crack I use is called kmspico. It installs a virus that when you boot up it stops Microsoft from checking activation. Has worked for many years.
I’ve not had to reformat. There’s another program called heidoc that downloads the installer from Microsoft, since they make you supply a product code through the website.