Dirsync must be installed on a x86 server. (2003/2008)
Dirsync does not support proxy that requires authentication
Check the server first if there are any existing SQL installations, since Dirsync installer will install SQL 2005 express automatically. (And crash) If it crashes then browse to the dirsync folder under program files and complete the MIIS installer and pointing it to the created SQL Instance (MSONLINE). Once it completes successfully logoff and on again. Then run the uninstalldirsync.exe.