MD 2011 - Restoring Backup
Moneydance 2011 and earlier versions can be set up to save backup files, and can automatically save the last 5 backup files in the same location as your data file.
These backup files are regular Moneydance files with either the date or a tilde (~) appended to the '.md' file extension, to keep you from confusing them with your regular files.
To open such a backup file, simply rename it so it ends with .md
Then you'll be able to open the file as normal, and access your data as it existed in Moneydance at the time the backup was made.