The official Client is up here, the only thing it does is a download manager for the full client:
You can get the download manager here if the above does not work:
If you are experiencing the “Side by Side” error when attempting to load the game, download the following C++ runtimes. They should resolve the issue.
Side by side error fix: http://mirror.irowiki.org/ragnarok/fullclient/vcredist/