We already mentioned in January that MSN Calendar users will be moved to the Windows Live Calendar service. This migration of existing MSN Calendar users to the Windows Live Calendar service will start in March. Windows Live Calendar does not support attachments to meetings and appointments. These will be removed from all meetings and appointments during the move. The Windows Live team recommends you save the attachments prior to March 1^st, 2009. If you have been using Outlook Connector 12.0 to synchronize Outlook with your MSN Calendar, you may also be able to retrieve/download a copy of the attachment from the event in your Outlook calendar.

Speaking of Outlook Connector: 12.0 users will be required to upgrade to the 12.1 version, which connects to Windows Live Calendar, starting February 24^th.  Starting that date, if you haven’t upgraded already, you will be prompted to upgrade when you boot Outlook and try to sync your Hotmail account. Of course you can upgrade now too if you want, but make sure your calendar is synchronized with the MSN Calendar service before you do so. Whichever way you choose, please restart Outlook after you upgrade so the add-in will be installed correctly.

More information about this move and how to make sure everything migrates smoothly can be found in this blog post and the FAQ.