PHP does not load the php3_mysql*.dll on startup.

The php3.ini (c:\windows\php3.ini) looks like:
....
;extension=php3_mysql.dll
extension=php3_mysql1.dll
;extension=php3_mysql2.dll
....

PHP 3.04 does load the module with this ini file, however, version 3.0.13 fails. 
I have exchanged all files between versions 3.0.13 and 3.0.4 several times but this error remains and it does not change if I modify the ini like this:
....  
extension=php3_mysql.dll
extension=php3_mysql1.dll
extension=php3_mysql2.dll
......

However,when other changes to the ini file have the effect expected. So the ini file works fine but the mysql lines in the file don't work somehow. 

Regards, Frank