I think this might work - When you are in MM2 on the preview panel there should be a small icon that looks like two frames with a dashed line seperating them (when you hover over it it says split the clip at the current frame or something similar). This should then give you two clips in the collections area., and you can delete the one you want. This can also be achieved from the menu bar (>clip>split).
You will then be able to delete from collections the bit you don't want. You could also chop up the remainder in a similar way. However with each of these clips you will have to "produce a movie", before you will be able to burn them to CD, as until you have done that they will only be a MM "project" file with a .MSWMM file extension.
Hope that helps but if you really want to get into MM some places to do a birt of reading are click here, click here
and click here