What you want is a
NLE.
Adobe Premiere Pro is an example of one.
AviSynth is a free, open source script driven video editor that you could use. Although their main site is down, you can still get the source from
SourceForge and compile it, yourself. Shockingly,
Avid has a free version of their profesionally NLE available for download. Finally, I'm told that Windows comes with
Movie Maker, which may be able to do what you want. I have never used it, myself...
Good luck!