and changes to php.ini don't seem to make a jot of difference you may find that your php.ini is not being read and you are running on defaults. The good news is that Elsint's fix (dated 26-Sep-2006) still works for php 5.2.6 under Windows Server 2003 SP2, on IIS6, running php as an ISAPI module. Diagnostic: run a test file &lt;php phpinfo(); ?php&gt; Load this in a browser and search the results for "Loaded Configuration File".  This points to the .ini file in use, which I have found is not always the one I have been editing ... If your problem is with extensions: search for extension_dir in the phpinfo() results.  If the entry which follows is C:\PHP5, or some other directory which does not exist on your drive you may need the registry fix.  The alternative is to put the php.ini file somewhere along the search path, but this is not quite as clean. Background: If you run the installer packages: php-5.2.5-win32-installer.msi or php-5.2.6-win32-installer.msi and choose the default install directory the following registry entires are added (Note you have to have the double backslashes for the .reg file to work even though Windows reports it worked without them). Once you have the new registry key in place you may find it sufficient to restart the World Wide Web Publishing Service, which is also restarted if you take the slightly longer option of restarting the IIS Admin Service. If this works for you and you want to backtrack by undoing