Tool for cutting and joining multiple parts of a video
There are various tools that will do this, from the professional Adobe Premier type to Windows Moviemaker (or whatever the Live version is called now)

To be honest, a quick google will give you pages of apps from premium to FOSS. Give some of the free ones a shot, and if they don'tdo what you need, give one of the expensive ones a shot on its trial version, which most have.