I recently tried to upgrade from autocad 2000 to mechanical desktop 6.Upon trying to open MDT6, I received an error message;Acad has caused an error in AC1ST15.DLL and will now close.When I closed out the error message then I received the next message; ASOEHOOK.DLL file cannot start.I thought that I had purchased corrupted software so I reinstalled autocad 2000 but started receiving the same error messages when the software had previously run with no problems.I was wondering if I needed a Registry Cleaner software but I'm looking for advice period.Thanks