Could anybody help me with this problem?

"PHP Warning: Module 'mysql' already loaded in Unknown on line"

We have a Windows 2003 64x running Moodle and Joomla however since installing joomla I've had to turn on the extension=php_mysql.dll in my PHP.ini. But now when I'm logged into moodle it returns the above error message.

Has anybody resolved this problem or could the advise me on what next to try...

Regards

Matt Gibson