Hi, my brother currently has a pc with Windows 10 pre installed since he bought it but has been having a lot of problems with the OS and interface ect and wants to downgrade to windows 7. Is it as easy as putting a windows 7 install disk into the computer and running it or is there pre requisites ect because every article I've read online is different and I don't want to mess up his computer lol. Also I have his Windows 10 product key aswell as a new bought Windows 7 disk and product key. Thanks