If you've tried to install the Windows Azure Active Directory Sync Tool and were met with an error about it already being installed, here are the steps I took to get it installed again after some blood, sweat and tears. Sorry for hitting you with another link instead of step-by-step instructions, there's just too many. Good luck.
1. Uninstall Forefront Identity Manager Synchronization Service (if already installed).
2. Follow instructions at: social.technet.microsoft.com/.../3f58170b-e455-4cd1-9e2f-57759df8aeb8
Another resource: community.office365.com/.../24384.aspx