user friendly revision control system

Solution 1:

You said you tried subversion, but did you ever try Tortoise SVN? It works as a shell extension and your repository can be anywhere (including locally in a directory).

It's fairly intuitive (a lot more than command line subversion). I'm not sure if the internal "diff" utility would work with things like word processor documents, but I'm sure that info is available somewhere.

Solution 2:

What about Dropbox? It uses a system of folder synchronising, but they also stores a copy on their own servers. It seems to be very easy to use.

Solution 3:

You may want to look at Git along with SmartGit both open source and the SmartGit UI is easy.

Solution 4:

Do you know about Shadow Copy? It's built into Windows.

Solution 5:

Have you looked into FileHamster? I've used it before and it's pretty easy to figure out.