Error message problem solved ... getting closer!
This is what I did: I got rid of PHP 4 and installed PHP 5. I still got the same message, but I copied php_mysqli.dll and php_mysqli.dll in the windows folder and now the message is no longer showing. (I couldn't do that with PHP 4 because those files are not included in the zip package)
BUT, I created a db in mysql, did a test, and just showed a blank page, not even an error message ... what is happening now??? The test query is this:
$query="SELECT * FROM tabla1";
Any ideas? Thanks very much!