HTTP 400 Bad Request

Hi all, I am fairly new to this (attended a beginners course last week) and I have been asked to install PHP on or 4 web servers (spread over 4 sites), all the servers are exactly the same running Windows XP and IIS 5. I downloaded the latest PHP 4.3.7 and managed to install it perfectly on 3 of the servers the last one that I tried all seemed to install correctly but I keep getting HTTP error 400 Bad request. Someone suggested going to the C:\PHP directory and creating a php document in there called test.php with <?phpinfo();?> to test I did this and PHP is working so I am baffled now. The only difference I can see with the output of the file on a working server and the one that is not working is the Configuration File (php.ini) Path on the server that is not working this is set to "C:\Documents and Settings\administrator.INTERNAL\WINDOWS\php.ini " and the one that works "C:\WINNT\php.ini ". Where is the path set? I installed PHP one each server using the same logon account? I hope someone can help as this is starting to drive me mad. Thanks Stephen