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Unfortunately, there's not a whole lot out there in terms of "free" video editing software. So far, the only common free editor I know of is Windows Movie Maker (or Windows Live Movie Maker). If you want an experienced video editor, then I could suggest Pinnacle Studio, which is a decent video editor and not too expensive either.
You're kind of out of luck when it comes to free software. Well, it depends on what you're using it for I suppose. For simple trimming and stuff I found a free setup that works well, but it's very tedious if your computer isn't built for a bunch of rendering. There are cheap options though. In the sub-100 range there's Pinnacle Studio which I hear is somewhat decent, and both Adobe and Sony offer stripped down, more essential versions of Premiere and Vegas respectively.
Movie Maker. I hate the layout for the program, but it has some decent render options. And like others have said, there's not many free video editing software out there, and the ones that are free are just about as good as Movie Maker is. If you don't need more than 1 track of video then you should be good.
I used Windows Movie Maker before i started getting the black video screen problem. I don't currently have any video editing program on any of my computers because i don't need it, but if i would, i would just buy Pinnacle Studio because it's the cheapest.
I personally use Avidemux. It's free and open source.
Other free alternatives: Openshot (open source) Lightworks (supposed to be open sourced, but I haven't kept up)
Lightworks has gotten some serious usage in the real world from what I've heard