if you were using MSN Calender and I dont know anyone who was you should take note there  moving the service over to live calender and you will have to do some work for the migration..

Q: What is happening?
A: MSN Calendar will be retired soon, as it is being replaced by Windows Live Calendar. If you have not already started using Windows Live Calendar, your calendar information will be moved from the original (MSN) calendar to the new Windows Live Calendar. As soon as everyone has moved over, the original (MSN) calendar will retire.

Q: When is this happening?
A: Your calendar data may be moved as early as March 1, 2009, after which you will no longer be able to access your original (MSN) calendar. The original (MSN) calendar is estimated to close on July 1, 2009, at which date we anticipate that all users will have moved to Windows Live Calendar. NOTE: the final close date is subject to change.

Q: What do I need to do?
A: We’ll do most of the moving for you; we’ll move over your appointments, meeting requests, tasks, and notes. However, if you have attachments in your original (MSN) web calendar, please save the files from your calendar to your computer by March 1, 2009. After March 1, 2009, you may no longer be able to access your attachments.

Q: What data will not be automatically moved over to my new calendar?
A: Deleted items (such as items you deleted from your original (MSN) calendar and items older than 3 months, which are automatically deleted from the original calendar) will not be moved over automatically. Additionally, if you have added attachments (like presentations, documents, and spreadsheets) to your calendar through Microsoft Outlook Connector or the MSN® Premium desktop client, your attachments will not be moved to your new calendar. If you have attachments in your original web calendar, please save the files from your calendar to your computer by March 1st, 2009. After March 1, 2009 you may no longer be able to access your attachments.

If you use the Outlook Connector to access your MSN Calendar, please see important update information here: Outlook Connector and migration to Windows Live Calendar

There is some really cool things happening around live calendar stay tune.