If you're using Windows, then you can do it with one of the built in apps for free. Unintuitively the option is in the 'Photos' app, not the 'Films & TV' app that you use to play back videos, but that's Microsoft for you!
Right click the video file, choose 'Open With...', then Photos. Once open, click on the icon on the left of the bar at the top of the screen and that will open the Trim function:
Drag the sliders at the bottom to remove the bits you don't want and click Save As - by default it will save the new video to the same folder, but add the word "Trim" to the file name, so you still have the original.