Hi - I got it to work with php 4.06, but I guess it works for 4.2.1 also.
Check these:
1)
Open php.ini and find under [path] and change to right extention path:
extension_dir= "c:\WebServer\php\extensions"
2) Load PHP as a module - not using the php.exe
#ScriptAlias /php/ "c:/webserver/php/"
#AddType application/x-httpd-php .php
#Action application/x-httpd-php "/php/php.exe
LoadModule php4_module c:/webserver/php/sapi/php4apache.dll (Insert)
AddType application/x-httpd-php .php (Insert)
I took it all from my site at www.mdz.dk - you can find more info there.
Greets Mads