Installing Windows 8 is a bit different than installing the previous version of Windows. Windows 7 you could install without entering a product key, but when you install Windows 8 you are required to fill in a key right-away. For a normal installation that doesn't matter much. But if you only want to experiment with Windows 8 for testing purposes, or for any other reason only will have it installed on your computer for a brief period, then it's a different question.
There is a lot of free Microsoft software to be had, programs which enable better web surfing and help protect against spyware are just two types. PCSTATS Tips