Here is some note about installation together php4 and php5 on apache2.
First you need is to edit with the help of hex editor php4apache2.dll (in my case, or php5apache2.dll) in php4 directory.
You find "x-httpd-php" and replace with "x-httpd-plc" e.g. (I found 2 matches)
Save your dll file and edit your apache config (httpd.conf) e.g. like:
PHP 5
LoadModule php5_module "C:/php_5_1_2/php5apache2.dll"
AddType application/x-httpd-php .php5
PHP 4
LoadModule php4_module "C:/php_4_3_3/sapi/php4apache2.dll"
AddType application/x-httpd-plc .php
And that is all! =)
If you run .php file -php4 is used, .php5 - php5 working...
Thanx for attention , Good lack!