You can download a free copy of Voyetra's old DOS Sequencer Plus sequencer and export the .sng files as MIDI files that you can then load into any MIDI sequencer. You can find the program at
ftp://ftp.voyetra.com/pub/voy/seqplus/seq_gold.zip Note you won't be able to to play the MIDI files from this program as it won't support your Windows MIDI hardware, but all you need to do is load the .sng files and then export them out as MIDI files. From what I've read online you should be able to do this.
[This message has been edited by Nigel (edited 06-28-2005).]