If you're caught using PHP4 on Windows and have been seeing some issues with the older MySQL libraries you've been using lately, it might be time to upgrade. "But I can't move away from PHP4," you say. No worries - this new post from Edin Kadribaaic should have the answer you're looking for.
Since the main PHP 4 distribution cannot be updated with the latest MySQL libs for various reasons, I will provide downloads of the latest PHP 4 with the latest MySQL libs.
His archive contains two files, both DLLs to replace the MySQL libraries that already exist.