upgrade imap dll problem

Hi, I have just upgraded a client server from 4.3.1 to 4.3.3, the server is = running Windows NT SP6. I upgraded by downloading the Zip file and = simply unzipping over the top of the old install. The webserver is on = drive C, and PHP is installed on drive D. After the installation however = I am getting the following error: Unable To Load Dynamic Link Library 'd:\php\extensions\php_imap.dll' the = specified module could not be found. Eveything else seems to work fine, and phpinfo() reports version 4.3.3. I have copied the extensions into the WinNT and WinNT/System32 = directory. I have tried modifying the php.ini file to point to the = correct path.. all to no avail. If anyone has any idea how to resolve = this issue I would be most grateful. Regards, Gareth Thomas