Reinstalling windows VS running 2 versions

[CallMeIshmael]

I want a clean version of windows (essentially one without any registry entries from software I currently have installed)


If I reinstall windows into its current directory, what exactly happens? Are these entries all removed? I have to reinstall all software, yes? But other files remain?


How does this compare to just installing windows onto a secondary hardrive?

[RandR]

I have both Windows Home and Windows Professional on my laptop. I installed the 2nd in order to use some free trials that had expired on my primary Windows, this worked fine. You will have an option of which one to load when the computer starts up, and if you have the space I would recommend this option.