It's great that you had success with that, but many players will not. In many (not all) cases, a System Restore will only thoroughly restore system files, not the state of programs and game installs. It can depend on the type of restore points that the system is establishing. What many players unfortunately will end up with is a broken game and other damaged programs.
I would have suggested CCleaner or perhaps a different install and registry cleaner tool first to undo a stuck partial install like that -- probably also with a partial success rate, but less chance of messing up other things along the way.
