Not sure if this is a better fit for the MySQL forums or PHP forums... So hopefully the right eyes will catch this.

I've got a remote MySQL server that I do not have access to upgrade. It's running an ancient version of MySQL (4.0.20). From what I can tell, I need to configure my Windows PHP install to use php_mysql.dll. However, this dll seems to be wiped from any official pages and I'm not entirely sure it'll even work with PHP 5.3.

I was originally getting FastCGI errors (The error code just says 'Unspecified error'). After throwing php_mysqli.dll into my PHP directory, I'm now getting mysql_pconnect is not a valid function (php error).

PHP version 5.3.0, IIS 6.0, Windows Server 2003, Ancient Mysql 4.0.20

Any help would be greatly appreciated.

Download the PHP Windows Zip package (not the installer), it will have the php_mysql.dll . There is a libmysql.dll file that will be in the root PHP director that needs to be accessible by the system (either by including your PHP directory in PATH or putting the file in a directory already in your PATH [eg. %windows*/system32])

MySQLi is a different extension. First it is for MySQL version 4.1.3 or higher. Secondly, the functions all begin with mysqli_*.

While you may not have access to upgrade, it is important you get the administrator to immediate upgrade their MySQL server. Using such an old version does not only pose security risks, but data integrity risks for your data. I urge you to keep backups as well. That release is over 6 years old.