I was getting the same error on Vista using Apache with PHP 5.2 and Wordpress 2.5.1. I manually created a wp-config.php file, which got my past that problem, but then I got an error complaining about not having MySQL installed. The problem in this case was that my configuration was not complete. This is what I did to get past it:
Added my php extension directory to my PATH (c:\php\ext)
Edited my php.ini file and made sure that the following two lines were uncommented:
extension=php_mysql.dll
extension=php_mysqli.dll
Once I did that, I could login to Wordpress, though now I'm only getting a directory listing of files, but that's just another config issue to overcome. I don't know if this will be helpful with your configuration, but hopefully it will.