Where is the source from... did you record it using an md-recorder, or was it transfered by usb from your computer? If the former here are the methods available to you:
1. Buy the new sony rh1 for over 300 bucks and upload through usb using sonicstage 4.2 (for pc)
2. Buy an md player with a digital out and record into a digital sound card in real time onto your computer
3. Run an analog line from your md's headphone jack into the analog input on a sound card, and record in real time onto your computer
Allot of help can be found on the minidisc forums:
http://www.minidisc.org