The machine or sound card's maker. If still broken, take it up as a warranty issue.
I use music composition software on my pc (which is less than a month old). Somehow the MIDI playback has gotten out of tune!--it's slightly flat. If the music plays through a MIDI keyboard instead of the speakers, it sounds fine. The default MIDI playback device is "Microsoft GS Wavetable SW Synth."
I re-installed (Windows XP Media Center Edition) but the default device is still out of tune. How can I correct this?