Ok, Banged my head on this one and found this tip courtesy of Matthew Cosier

If you are getting the Error "The language is not supported on the server" when you are installing MOSS 2007, you have most likely uninstalled the product previously. For some reson, it doesn't set the registry key appropriately when it is reinstalled.

In order to fix the problem, you need to restore the ServerLanguage registry value by creating the following .reg file (open notepad and paste the following):

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Shared Tools\Web Server Extensions\12.0\ServerLanguage]
"1033"=""

Save this as fixlanguage.reg and upload it to your server. Double click the file and say yes to the prompts.

Rerun your SPT configuration wizard, and you will no longer see the error.

Worked for me.. Thanks Matthew !!