This is a neat trick. I've been transferring VHS tapes to DVDs for patrons. One of them wanted to send just a 30 second bit to a friend.
Movie Maker used to be my goto program for such but lately has been declaring files as "corrupted" without reason. I know Microsoft is phasing out the program so I looked at that old workhorse VLC. Amazing program, didn't let me down.
Pretty simple. Open up the file in VLC (right-click and Open With…), under View —> Advanced Controls. Once that is activated, you will see some new icons above your usually controls down at the bottom. The one to the left is 'Record'. Play your file, and when you want get to the part you want to separate you hit 'Record'. When you are done you hit 'Record' again. The copied bit will now be in your Videos folder.
Smooooth.