Question:
I am having difficulties getting my Windows PC running Vista/Win7/8 to output MIDI to my Kurzweil via USB. Do I need to install a driver?

Answer:

No. The current line of Kurzweil products have a standard class-compliant USB-MIDI implementation. They do not require the installation of any additional drivers.

Some background to be aware of:

Microsoft has been steadily REMOVING MIDI FEATURES from Windows since Vista. In Windows XP, Microsoft provided a MIDI Mapper control panel which allowed end users to select a MIDI output device. Since Vista this has not been available. As such, certain apps (like Windows Media Player – WMP) can no longer play MIDI songs triggering external MIDI devices because WMP is only routed to the internal Microsoft GS Synthesizer.

This means the MIDI app you choose to use must natively offer its own built-in MIDI mapping abilities OR you could possibly install a 3rd party MIDI mapper whose purpose is to replace the MIDI routing abilities removed from Windows. Fortunately,
these days, most commercial MIDI software products for PC have a configuration screen which includes the MIDI device mapping necessary to route to an external MIDI device.