Auditing, Permissions, & File Deletion on Windows 8.1

I changed ownership of my C:\ in order to change permissions, be able to audit, and delete files which are locked. Usually system files are locked and I ignore those when prompted that they cannot be changed without admin approval (even providing admin approval doesn't allow their modification). I'm wondering what I have to do to be able to make decisions on my own system? Does anyone know a good step by step guide? My old Windows installation is taking up 17 gigs on my hard drive and I have a 230g hard drive. Needless to say space is precious with the size of downloads/installations being what they are (games that are 20g, Windows updates that are 3g..). Thanks in advance.