This .ZIP file is simply an archive of a driver CD provided by the manufacturer. It was written for the 1997 Ensoniq AudioPCI 9741 6000566 sound card.
First remove the sound card entries from your Device Manager. Next, choose Add New Hardware. When Windows asks where to find the driver, let it search the directory where you unzipped the files. It should detect your card as an Ensoniq AudioPCI and install the necessary drivers and .INF files. If you can't get it to work this way, run SETUP.EXE from the directory you unzipped the files to.
These drivers work perfectly, yielding no MIDI device errors. Good luck. -Ben