Configure Report Server Error

its common...you need to have a valid server connection
in the reporting services configuration --> database setup --> select the servername and click the connect button next to it...enter the credentials type properly and give ok...(use either user - integrated security / sql server account - just try both options) and in the database name...click new and enhter the details...say ok...
select SERVICE CREDENTIALS in the crdentials type(below to the database name) click apply...let me know the result...

jaiganeshsrinivasan, I tried your suggestion but still no luck.

This is the error I get when I create a report and run:

The version of the report server database is either in a format that is not valid, or it cannot be read. The found version is 'C.0.8.54'. The expected version is 'C.0.8.40'. To continue, update the version of the report server database and verify access rights. (rsInvalidReportServerDatabase)

you have to choose the SAME instance of database for your report server...like try with a proper instance name...

Make sure under Security/Roles - that the RSExecRole exist, if not then make one. It should also be assigned to the schema of RSExecRole. On your report service login User make sure that this user is assigned under the RSExecRole.

Which one do you mean should be assigned to the schema of RSExecRole?

can you check in your sql server whther the database ReportServer already exists ? or is not created at all !!!

as mentioned earlier...the INSTANCES have to be the same for SQL and reporting...so tht might have fixed it...
you dont need to uninstall...but you would have acreated a new instance of the sql server adn it should have worked...