If you are trying to sync Apple MobileMe with Windows, be aware of some limitations. First, contact syncing will only work with Outlook 2003 and 2007, Outlook Express (Win XP), and Windows Contacts (Vista). You can only sync calendars that are in Outlook 2003 and 2007, and bookmarks can only be synced with Safari and Internet Explorer. (Sort of get the feeling that Apple wants to exclude Mozilla?) You also need the most up-to-date version of iTunes. See more troubleshooting help at Apple.