How to Get Rid of the Factory Junk on a Computer

Most computers come with all that factory junk, and most people just never bother to clean it out. And so you end up with a severely governed, slash crippled machine. Ye, in my opinionye, i know when i've built pieces for the church, one of the first things they do with a brand new computer right out of the box is go in into a factory re store on it. It strips a lot of the extra stuff off of it. But people always look at me funnily, you just turned it on. Why are you destroying it? Like i'm starting over to get rid of all the croft.