If all you want is to play midi files, Ziff-Davis has a utility called Midi Colors that will do the playing for you for about $10.00 (but check the price before ordering). There are several free programs that will do the same, but this one has some features I've used for years and that I find very helpful when converting midi to notation.

A cute feature of this program is that it displays a keyboard for each midi channel, and you can turn any channel(s) on or off, to see (and hear) what each "voice" sings. You also can vary the speed for the playback, if you're a little slow like I am and need to hear the individual notes more clearly. (Some Bluegrass midis sound more like a buzz saw than like music, as recorded.)

I'm currently using the version that I got when I was running Win95 (it was free then), and it works fine in Win7. It's been on every computer we've had since Win95.

Windows Media Player, as in Win7, apparently doesn't include a midi player capability as a default, so you do need to add a midi-capable program. Almost any notation program whould do what you want, with the exception of a few ultra-trashy things that don't allow "Save-As .mid" and/or "Import .mid." We've had no problem using the notation programs we had with WinXP and Vista in Win7, but that may not be the case for all older programs.

Stated crudely (and not too accurately), you need a program that can make a midi in order to play a midi.

Once you get a program with midi capability, any sound card should suffice, since it's the midi file "translation" of the .mid (a text file) to pitch/duration/loudness language that matters, and any card should understand what to do with it once it's "made digital" in an appropriate audio format.

John