I have a Creative Audigy SE sound card, which provides hardware MIDI synthesis. However, under Vista, there was no way (that I could see) to change the default MIDI output device to this card, meaning that all apps were using the software synthesiser instead.
Vista MIDI Fix is a 10-minute application I wrote to let me easily change the default MIDI output device. Applications which use MIDI device 0 still end up with the software synthesiser, unfortunately.
To get the hardware MIDI output device available I needed to install Creative's old XP drivers, and not the new Vista ones from their site. This results in missing CMSS, but other features - such as bass redirection, bass boost, 24-bit/96kHz output and the graphical equaliser - now work.
The Creative mixer either crashes or only displays two volume sliders (master and CD audio), which means that (as far as I can tell) there's no easy way to enable MIDI Reverb and MIDI Chorus.