The "round thing" is a Griffin "iMic." It needs some software
that you apparently didn't inherit.
Various sound capture-edit apps work with iMic. I know Amadeus II
and CDSpinDoctor take iMic input. Amadeus is shareware from
versiontracker.com and is my editor of choice. Spin Doctor comes
with Toast.
The Griffin product is FinalVinyl, free from
http://www.griffintechnology.com/sof...ware_imic.html
You fire up one of the above apps, set it to "preview" the incoming
sound, start your minidisk playing, make adjustments as necessary
to "sound right," then restart the minidiask player, and hit "record"
in the app. This brings the audio into the app, after which you can
save it in a variety of formats.
Hope this helps.