We all have Windows machines but store all our files on a NAS drive, so we don't really have a server, but want to use some kind of version control.
Can anyone recommend a version control software to use and a simple tutorial on how to install and use it, or if not suggest a book to buy that will talk me through it step by step.
You can use the VisualSVN Server and store repositories on a network share (NAS).
Follow the steps provided at Storing repositories on a network share to setup VisualSVN Server to store it's repositories on a share.