Confused over php_mysql.dll

Hi (again) Now that I have learnt to type correctly, I have Apache 1.3.12 and PHP4 running OK on my local machine (Windows 98) but I am now having problems with MySQL. If I uncomment "extension=php_mysql.dll" in PHP.INI (which I presume I do), the phpinfo page hangs again in the browser. I have tried loading the page with and without MySQL running but get same problem everytime. What confuses me is that no file called "php_mysql.dll" came with PHP4 to stick in my windows/system directory but php3_mysql.dll does come with PHP3. I have read that PHP4 has certain functionality built in but then why call to an external file which isn't there ? I am now going to hack around and try and find the problem but if anyone can help me, I would be very grateful. Thank you in anticipation Tim