In your httpd.conf file you should have the following lines:
ServerRoot "C:/Program Files/Apache Group/Apache2"
Make sure that is pointing to the correct folder.
DocumentRoot "C:/Program Files/Apache Group/Apache2/htdocs"
, make sure this is correct.
#
# This should be changed to whatever you set DocumentRoot to.
#
<Directory "C:/Program Files/Apache Group/Apache2/htdocs">
that's about it. If you want to install PHP as a module, you need to add something like this, changing paths and the php dll accordingly:
LoadModule php4_module c:/php/php-4.3.10-Win32/sapi/php4apache.dll
PHPIniDir "c:\php\php-4.3.10-Win32"
This way Apache looks for PHP ini in the above folder - you don't need to copy it to your system directory.