Good point. Seems some explorer versions don't seem to like this. Still very easily solved: win-r (opens 'execute' window), then enter "cmd" (without the quotes). cd %appdata% ren minecraft_bck .minecraft And done. The last 2 entries are commands which you need to enter in the command line window that got started.
Hmm, that's a good solution. I, however, don't think most people know this, so it'd still be best to just avoid the issue in the first place I'd say. Anyways, whoops, went slightly off topic there. Let's just wait for the answers to the questions, and we'll see if we can help from there.