You should make regular backups of your MSDE database in case of server failure.
To back up MSDE
1. Shut down ListManager. If ListManager is running in a console window, ctrl-c will begin the shutdown process. If it is running as a service, stop the service by navigating to Start -- Settings -- Control Panel -- Administrative Tools.
2. Shut down MSDE using the SQL Server Service Manager. It can be found by clicking Start -- Programs -- MSDE -- Service Manager.
3. Using Windows Explorer (Start – Programs – Accessories – Windows Explorer), In the left Navigation bar, click the SQL Server Data Directory:
C:\Program Files\Microsoft SQL Server\MSSQL\Data\ListManager_Data.MDF
C:\Program Files\Microsoft SQL Server\MSSQL\Data\ListManager_Log.LDF
4. Copy the entire data directory to your backup location.
5. Restart MSDE using the SQL Server Service Manager.
6. Restart ListManager.
To restore your backup
1. Stop ListManager.
2. Copy the ListManager_log.ldf and ListManager.mdf files from the backup location to the data directory of your MSDE installation.
3. Restart MSDE.