It is possible to replace the Fedora installation with CentOS and leave the Window installation in tact. I mention this only because of the use of "trash", "start over" and &q... [by azjp]
I am currently in a situation where I am trying to install CentOS 7, however when booting into the installation it get into this [CentOS "core"] environment which I am assuming is a minimal installation of some sort. Typing "startx" says the command is not found. :( ...Anyway, the USB media that I used to install was prepared using Unetbootin on Fedora 20.