Hi Pillmaker,
If you are using the Msn software to send and receive your emails in your inbox you have an option were you can save your folders on the computer in the left pane. Please ensure you take a back up of emails that are saved on Folders on computer if you are trying to uninstall and reinstall the Msn software. Or move your emails back to Folders on Msn so that it can be stored on the server side, so that you do not lose any important data, please check the link below for more information regarding the back up of emails
How to backup my e-mails using the MSN Explorer software?
http://answers.msn.com/solution.aspx?solutionid=d830f08c-414d-49ae-91cb-df58aa44832f
Please revert back for further assistance.
Thanks!