The user data and message history is stored in the QIE database. Deleting the QIE database would remove this data. For the QIE standard version, the database is located in the QIE home directory which is typically C:\ProgramData\QIE\h2. For the QIE Enterprise version, the database could be located in the QIE home directory or on an MSSQL, MySQL, or MariaDB install somewhere on the network.
To remove the entire QIE install delete the database as well as the QIE home directory which is located by default C:\ProgramData\QIE.
Note: A QIE license can only be installed on one instance. If the license is to be reinstalled or used on another instance of QIE it should be deleted before the uninstall. To delete the QIE license, log into QIE and navigate to Help About and then select the license to be deleted and click on Delete from the menu bar.