SQL server name mismatch

Our prod SQL server name from Query Analyzer shows as "prodsql6" by command "select @@servername, @@servicename" where as on enterprise manager it shows as "prodsql1". The host name is prodsql1. The registry entry (regedit) key of HKEY_LOCAL_MACHINE....MSSQLSERVER\DefaultDomain is "prodsql6".

Also query from WMI (Windows Management Instrumentation" Tester as "select name, clustered, package, versionstring from mssql_sqlserver" shows sqlserver name "prodsql1".

The SQL server is running fine on host prodsql1. How can I change the servername in the SQLSERVER so that query analyzer show the correct name.