Installing PHP 4.3 on Windows XP with SP2 and IIS

I am trying to install php 4.3 on Windows XP Pro SP2 w/ IIS ...
(please dont kill me :-))

 I am doing it via ISAPI, I am up to the step in the instruction sheet
that says "Under Home Directory, click on the 'configuration' button.
Add a new entry to the Application Mappings. Use the path to the
php4isapi.dll / php5isapi.dll as the Executable, supply .php as the
extention, leave 'Method exclusions' blank, and check the 'script
engine' checkbox.'

I did that... but it is not allowing me to click on the "OK" button... 

anyone have advice --- please dont tell me to get Apache :-P