Hi,
I am no expert on audio editing, but if you have some decent sound editing software (not MS Sound recorder) then it is possible - copy one part, paste it to a new file, then copy the rest and save it to a separate file.
I found that Nero WaveEditor (supplied with CD burning s/w) and Creative WaveStudio (come with sound cards) both work well, but neither can deal with MP3's direct - they have to be converted to WAV files then converted back to MP3 afterwards.
Remember that MP3 files are highly compressed, so the pc has to decompress the data on the fly, which is why most sound editors can't deal with mp3's directly.
John