php_mysql not loaded under Apache but is there in CLI?

All, I'm new to this news group - so apologies if I blunder. I've just installed Apache2, MySQL and php (5.1.6) under Windows XP (haven't tried this under Linux yet). When I access via Apache as http://localhost/info.php there is no MySQL support - and testing it further I get errors trying to log on to the database via the web server. However, if I use the CLI (e.g. php -i) the MySQL support is there - and I can connect to the database OK from the CLI. Both sets of info show they're using the same php.ini file, they ARE the same version. I can't see what's going on. Other loadable modules (e.g. php_gd) are loading as you'd expect in both environments - it's only MySQL that's affected. Any help with this would be much appreciated. Thanks in advance, theBrem.