You'll find the file here...
Win7 & Vista is in C:\ProgramData\Battle.net\Agent
WinXP is in C:\Documents and Settings\All Users\Application Data\Battle.net\Agent
Just type that link into your Internet Browser and select the Agent database file, then open it with wordpad.You'll be looking for the following sequence:
Change it to:
There will be three instances of it, you need to update all of them.