"The report server database is not a supported compatibility level or a connection cannot be established."
- Go to Start > All programs > MSSQL Server 2008 R2 > Configuration Tools > Reporting services configuration manager.
- Click on Connect button on the Reporting services configuration connection window.
- Click on Database tab from left hand pane and click on Change Database button.
- Select radio button Choose an existing report server database and Click on Next button.
- Under Server name box, enter the correct SQL Server name, keep other settings default and click on Test Connection button.
- Once Test Connection succuessfully esatablished complete the wizard.
Are you facing reporting service related error while reinstalling SQL server? Please refer to Accuweb > Reporting service error for more details.