I had Em Client version of 2013, made backup’s time to time. Finally I have reinstalled W7 and now I have Em Client version of 2016. Can not restore the back up. Backup contains .dat files. It seems Em Client proceeds restoring data but finally I can not see any previous information only emty Em Client window. Please advice

If you are using Win 7 then you should go with Outlook, import all the eM Client backup in Outlook by using this tool http://www.birdiesoftware.com/em-client-converter/