Changing the 'Server Collation' after installation

Question

I want to change the Server Collation of SQL Server 2008 R2

As all opinions says (including MSDN) the following command should be executed:

E:\setup.exe /q /ACTION=RebuildDatabase /INSTANCENAME=MSSQLSERVER /SAPWD=”**″ /SQLSYSADMINACCOUNTS=”HEREISMYPROBLEM” /SqlCollation=SQL_Latin1_General_CP1_CI_AS

As I Pointed, my problem is with the SYSADMINACCOUNT paremeter because the error that I get is:

The Windows account ”blablabla” does not exist and cannot be provisioned as a SQL Server system administrator.

I tried all possible windows accounts that may be, but It's not working. Please can you guide me how to know my correct windows account.

The MSDN link that shows this problem is here

Answer 1

This page describes the switches and says to use "DOMAIN\User" format, for example:

BUILTIN\Administrators MyDomain\MyUser