lammert - 1:46 am on Oct 5, 2010 (gmt 0)
Hi WideBlace, first of all Welcome to WebmasterWorld!
Apache normally maintains error log files with messages of what doesn't go right internally. You might first look there to see if that gives more information.
The second thing which comes to my mind is that dhe php_mysqli.dll exists, but that the PATH setting for the Apache service doesn't contain the directory where the dll can be found.