I know there are other questions about problems with PGSQL not loading, but I haven't found a solution that works for me and directly addresses an IIS setup under Windows (obviously). Using PostgreSQL 8.4.
Since I am a complete novice in PHP (only trying to get MantisBT to run) I find this extremely hard to debug/research.
I've set the path to both PostgreSQL bin folder and the PHP folders (v5.3 subfolder first and the PHP root after that). I've checked that libpq.dll is present in all three of these folders and I've tried copying the libpq.dll from the PostgreSQL folder to both PHP folders. I've made sure php.ini contains
extension=php_pdo_pgsql.dll
extension=php_pgsql.dll
in both PHP folders (root as well as v5.3).
What more to check/try/examine?