Sometimes you might want to break single tracks in your iTunes library into smaller tracks. For example, you might have imported a CD with a hidden bonus track at the end, where a long period of silence connects the bonus track to the last song on the CD. The last song, the silence and the bonus track show up in your library as a single track ... but you might prefer to have the songs as individual tracks and lose the silence altogether.
Here's how you can do that using iTunes for Windows. (Note that this technique will not work on older tracks with DRM purchased from the iTunes Store. It should work fine with more-modern "iTunes Plus" tracks purchased from the iTunes Store.)
In your library window, right-click the track you want to chop up, and select "Get info":
Go to the "Options" tab. Set the "Start Time" and "Stop Time" corresponding to the start and finish of the chunk of song you want to chop out, then click "OK":
Right-click on the track again in the main library window and select "Create XXX version" (the XXX will be whatever file format you happen to have set in your iTunes Importing preferences at the time):
After a little while, iTunes will spit out a second, smaller copy of the track, containing just the music between the Start and Stop times you set in the original track. (Rename the new track if and as you please.)
To chop out a different chunk, go back to the original track again, reset the Start and Stop times again, and "Create XXX version" again.
If you want to keep the big original track in your library, and you want it to play normally, just go back into the "Options" tab again, uncheck the boxes next to "Start Time" and "Stop Time", and click OK. This will return the Start and Stop times of the big original track back to their default settings.
Tweaks to the Technique
if you want to cut down on the possibility of audio quality loss, import the track (that you want to chop up) into your iTunes library in one of the uncompressed formats (WAV or AIFF), and then change your importing preferences to a compressed format (AAC, mp3 or Apple Lossless) prior to doing the chopping. For advice on converting file formats, see the following document: