Hi,
I'd suggest to try the sapi version of php by adding LoadModule mod_php4 <pathto/php4apache2.dll>
Besides that php4 in general is very unstable on apache 2.x. php-4.1.2 is more unstable that 4.3.2.
The best solution would be to use apache 1.3.27 until php 4.x becomes stable on apache 2.x.
I had several problems using php 4.x with apache 2 on Windows. I installed it several times and had problems on many of that installs. It sometimes worked without problem and sometimes I had problems like garbled form input names when accessing them with $_POST.
How did you try to access $php_self and what did you get as result ?
You might want to try the php extract function which can make e.g. posted variables globally available as $variable instead of using $POST (same for $SERVER).
http://www.php.net/manual/en/function.extract.php
Thomas