If you have a soundcard with digtial outputs you could connect a minidisk recorder to your computer via optical cable. The transfer is 100% digital.
Two soundcards come to my mind
M-Audio Audiophile 2496 http://www.midiman.com/products/m-audio/audiophile.php
Has coax in/outs and does NOT do unconditional internal resampling like the SBLive! for example. Very high quality, but coax is rarely seen on portable minidisk recorders...
Terratec EWX 24/96 http://www.terratec.net/products/ewx2496/ewx2496_overview.htm
Excellent as well, has optical in/outs but might be hard-to-get in the US (it's a German company). No unconditional internal resampling as well!
Both cards have great specs. and, which might be interesting to you, have SCMS (S-erial C-opy M-anagement S-ystem) control. This means that even if the data stream from say a CD or DVD is set to "no-copy" you can override this and copy it to your minidisc (or whatever you hook up to it)!
Mind that these are not gaming cards like SBLive and the like, so they don't feature fancy midibanks and childish EAX surround stuff and all that...
However, it is possible to transmit Dolby Digital or DTS data streams to external decoders (nice if you want to watch DVDs from your PC).
The cards are a bit pricey (around 170€ in Germany for the EWX, the M-Audio is around 255€ here, should be a lot cheaper in the US though)´, but are top-notch in terms of digital & analog quality in this price region (and beat the hell out of gamers cards, even the new Audigy from Creative).
edit: Notice how nice I evaded the ban on the word "S-erial"!