To find SQL Server is actually used or not?
SQL Server can log failed logins, successful logins, both or none to the SQL server log.  Check your current setting and if it is not collecting both failed and successful logins change it so that it is.  Once it's been running that way for a few weeks (preferably over a month end &amp; quarter end) check to see if there has been any activity.  If no one is logging in then you can run a final backup of your databases (you should probably include the master and msdb databases as well as the user databases).  Move those backups to long term storage and shut down the instance.  If no one complains after a while then you can de-com.

Under the server properties: