certainthings

If you open up the file, skip along to the bit you want. I think it's automatically set up so that the arrow keys skip ahead/backwards by one frame at a time, which is handy. At the bottom there's a row of keys, the two on the right are the ones you want-if you hover over them, they should say mark in and mark out. Click mark in where you want the bit to begin and mark out where you want it to end, and then it's file> save segmented .avi

I hope that helps and if not, lemme know :D