"Q: When I go to a MIDI site, I can bring up the page with no trouble but when I click on a midi or wav file the Media Player doesn't open and I get the message that this page cannot be displayed. If I right click on the MIDI link and "save target as" to my desktop I can play it from there.
A: Go to WMP's Tools:Formats:Options. Uncheck "MIDI File", click apply, then check "MIDI file" and click Apply.
Q: How do I trouble-shoot MIDI?
A: I don't know. WMP has nothing to do with MIDI, we just take advantage of the system's support for it. Wise Tess says:
* Make sure your volume slider for "Midi" (and/or SW Synth) is up and not muted.
* Make sure "Midi Sequencer Device" is loaded in Control Panel, Multimedia, Devices, Media Control Devices. You can add it from Add New Hardware, Next, Next, No, Sound/Video/Games, Microsoft MCI. If it is loaded, go ahead and remove it and reinstall it.
Also, this may help some XP users having troubles with MIDI."
from the WMP MINI FAQ