Jenk wrote:and if on Windows, copy the libmysql.dll and php_mysql.dll files into the C:\Windows\System32 directory, it will not work if they are anywhere else.
Not so, you just need to make sure you've correctly set your extension_dir e.g:
I did this a few days ago after reformating my machine, following the recommended install instructions in the text file for the PHP5 binary.
Also changed Apache to load my ini file from the PHP folder which has made upgrading and maintanence so much easier now that everything is in one place. (I upgraded to 5.1.1 the following evening)
Only trouble I had was loading the mysql.dll funnily enough. Everytime I restarted apache2 it couldn't find the dll despite the path being correct.
After rebooting the computer it worked fine. I guess the dlls hadn't registered when I unzipped the PHP package or something. I never went near the System32 folder.