Source control system for single developer

Question

What\'s the recommended source control system for a very small team (one developer)?

Price does not matter. Customer would pay :-)
I\'m working on Vista32 with V

Answer 1

I realize that cost isn't a problem but a nice free solution that wouldn't involve checking in and out would be to host the code within Dropbox by doing this you'd instantly get versioning and backup which are the main features that a single developer system would provide.