include_path and php.ini

Hi all, I'm trying PHP4 on Win200 professional, I've found out that if I put a php.ini file in a web site directory, this file override the set-up of \windows\php.ini; this is great, because I can set different php.ini for each Web site, and, for example, I can set a different include_path for each site. But this in Win98 doesn't work, Win98 looks only at the \windows\php.ini file, why? Is there another way to specify different php.ini for different sites? Thanks in advance.