you see minidiscs used in minidisc players come in a cartridge that slips into the player.
And most current players can't play data files, just .wav files.
I just use the digital (optical) line to connect mine to my sound card. You can also use a line out/in too, but quality here isn't as good as optical.
Some new minidisc players have usb support.
Sony i believe are creating a 1Gb minidisc that can also be formatted in FAT32 and used as data storage. These disks are going to cost just a little more than current 80min minidiscs. They are trying meant to take over this silly surge of MP3 players.
I'm not too keen on MP3 players as 99% of them don't even concentrate on quality of playback. All they seem to be doing is catering for storage size!
I've tried a few of these MP3 players that my mates have got, from iPods to whatever... and to be turely honest you may aswell be listening to a cassette walkman from the 80's! The earphones are naff, no quality bass and trebble control etc...
OK you can buy a decent pair of earphones and use them but it's no good using £50 earphones on naff player, believe me i've tried. Ok, so i'm probably just too fussy, but if i'm going to spend around £200 on a portable music device i'd rather it was quality! I always seem to get the latest quality sound stuff i can afford. If you're going to buy a minidisc player go for sony, they really do sound much much better over their competitors and buy a pair of MDR-EX71SL earphones from you're local sony centre (probably have to order them in).