Pavlovic,
Your problem is most likely cuased because, in your php.ini, you're loading dll's for which PHP4 currently has no support. Try commenting out all the Windows Extensions in php.ini. If you need more that just MySQL support, which is built-in, grab the PHP 4.0.1pl2 update from php.net. If that still doesn't give you the level of support you require, try download.swwwing.com. Also, unlike PHP3, you don't specify version in Apache's Action directive;
Action application/x-httpd-php "/php4/php.exe"
should read:
Action application/x-httpd-php "/php/php.exe"
Hope this helps!
Cheers,
Geoff