It is easy uninstall and re-install. Your p.c. also needs to have a sound card and speakers - most modern ones do. If you have a c.d. player, then you can probably get better quality sound if you run the output of your soundcard to your c.d. player. A Midi file is a kind of score that can be read by a synthesizer, usually much smaller than sound recordings. The best soundcards will play it using actual sound samples of a flautist playing a note.
Older ones approximate the sound of a flute as best they can.
You can download a software synthesizer for playing MIDI files. You can get one on 90 day free trial from Yamaha. I recommend this unless your soundcard is already top-notch. Musicians will be interested in Noteworthy Player, from Noteworthy Composer , which lets you see a MIDI file as a score. Here are some samples of the compositions that come with the program.