Upon trying to open the client, as it never truly opens, the error pops up and the details are the following: If you select the only applicable button, ‘Close’ the program closes. All the other buttons, obviously, are not really helpful.
System.IO.IOException: The process cannot access the file because it is being used by another process.
at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
The best option is to rename the database folder C:\Users_[__username]_\AppData\Roaming\eM Client. You may have to show hidden items in Explorer to do that.
When you restart eM Client it will be with a new empty database.
The database is the complete /eM Client/ folder. If you close eM Client and rename the folder, the next time it starts it will create a new /eM Client/ folder with all the necessary files.
A backup is a complete snapshot of the database at that time. Restoring from the backup will thus restore the database to exactly how it was when the backup was made. This completely replaces the existing database.
By deleting or renaming the database, eM Client will create a new database will all the necessary folders and files. This is a blank database, so none of your previous data like messages or events, and none of the settings, categories etc will be there. If your data was synced with an online service using IMAP or Exchange, and calendars and contacts are similarly synced, then after adding the accounts to eM Client the data will resync from the server.
Always a good idea to make a back before doing anything drastic!!