If Internet Explorer has problems playing mp3 or midi files (e.g. "Page Not Found" error), try the following fix.

In Internet Explorer, go to "Tools", "Internet Options", and click "Programs". Go to bottom of screen and select "Set Programs", then select "Set Program Access and Computer Defaults".  Click on "Custom" and then the down arrow to the right of "Custom". Scroll down and under "Choose a default media player", select Windows Media Player. Click "ok". Close and reopen Internet Explorer. The media files should then play with Windows Media Player (assuming it is set to play mp3 and midi files).