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Yesteday I lost 1.5 hours trying to install PHP 5.1.6 as Apache2 module on Windows. MySQL and MCrypt did not want to work. I even copied related DLLs to ext/ folder but all was useless.
Without believing to success I copied libmysql and libmcrypt DLLs to windows\system32 and... it worked! By definition it should work if all dependent DLLs are in the same directory but it did not for unknown reason.
Anyway, it works now and I am posting it here for those who can encounter the same problem.
