Wrong paramenter in JVM Arguments in Cognos Admin Tool! How to rectify?!

Hi All!
I am using Cognos Administrative tool for Cognos Report Studio. I have given the wrong hostname in “Additional JVM Arguments” for starting 'Query Service". Now I am unable to open the cognos administrative tool itself in the browser to change the hostname. Does anybody know how to resolve this? Could someone please provide the information regarding where the parameters we configure in Cognos Administrative Tool gets stored in the system, so that I may rectify this parameter?
Because of this, I am getting the error when I open the cognos admin tool in browser: “The user is already authenticated in all available namespaces.”