Here I am at my computer. You can just barely see the CPU at the right corner of the photo. I bought it many many years ago, as a Vector AT. It has survived six motherboard transplants. It has the original keyboard, but a fleamarket video monitor has been added. However, it is on its last legs now, on account of being in a primative AT case which ATX mother boards won't easily fit into. It is a sturdier case by far than the one which will replace it. That one sits in my basement as I populate it with rebate items from Staples and Office Max, and Internet close-out bargains. My thought is that the computer will be obsolete a few months after being bought, so why not start out with an obsolete one? Same strategy as buying a car with a few scratches on it -- you won't feel so bad when as it ages.
The music keyboard is called a "QuickShot Midi Composer". It cost $100 several years ago and came with an ancient version of Cakewalk Home Studio. The midi file that you may have played was done with this stuff. Elsewhere I have a 10 year old digital piano (Clavinova CLP-360) which also can serve as a MIDI keyboard (and does). Recently it needed a new "contact strip" -- I mention that because I have some experience now with the replacement of those things, and with the repair of keyboards of various kinds.
Sometimes it seems that MIDI, in the face of MP3 and similar, has come and gone. But MIDI is still alive and well on the Web. If you are interested, here is a place to start. Instrumental music played on a good wavetable sound card, or virtual synthesizer like one of the (Roland) Virtual Sound Canvas programs, can sound very fine. There is lots of good MIDI stuff out there on the web -- here is one I particularly like. Google will find a MIDI file of just about anything, but not that one, for some reason. The music industry does not take such an interest in copyright violations in MIDI as in MP3. MIDI files are very bandwith-conservative, but nobody cares about that anymore.
Update Aug. 2006: The CLP-360 found a new home, and there's now a Yamaha P90 in the "music room". The "Quik Shot" keyboard had a simple contact-strip cleaning, and is still going strong. Music software is getting some updates. I am still a fan of MIDI, and my Roland SCC card still functions (no latency), but needs an ISA slot. A recently-acquired computer now houses a bunch of wavetable synths, and one has learned not to notice the slight delays.
Where are my stereo speakers? Well, they are behind me. (That little thing on the top of the monitor is a telelphone amplifier). There is no reason not to use an existing audio system instead of little cheesey computer speakers, especially if one is going to play high quality sound files. And I happen to be a collector of old audio systems, stereo but not surround-sound yet. So I am a bit out of touch, so what?
Aug 2006: Still working on keyboard skills. Typing also is undergoing improvement. Fingers still limber, but knees in mornings take a while to get bending.