I have failed to mention this isn't for me, I'm building this for my parent's company who needs it for video editing. Mouse, keyboard, monitor, os are already covered by them. Yes I already have a case that a relative of mine gave me. As for software, I have no idea. I assume that it's only going to be minor video editing and not full blown professional hundreds of dollars of software. By small form factor, I am probably thinking that my parents mean ATX or smaller.