One of the most frequent questions I get from CNET Download.com users is "What free software can I use to edit video?" If I didn't respond to you personally, it's likely because there's not an easy answer. It depends on what type of video you have, and what you want to do with it.
The XP version of Movie Maker is adequate for putting together clips into larger videos, adding simple transitions, and making basic edits, but I can't recommend the experience. The review on CNET Download.com is overly harsh, but it encapsulates several problems you may encounter.
Unfortunately, Avid Free DV is no longer supported, but if you can find a version of it, the forums are still active. It was a complicated interface, but the included feature set was fantastic.
One app with loads of potential is the open-source video editor Jahshaka. The key word is "potential." The interface is daunting, and help is nonexistent, aside from outdated tutorials on the Web site. It was also ported from Linux and requires installation of the GDK platform and OpenLibraries, both of which are included in the full Jahshaka installer.
However, if you take the time to learn the program and actually read some of those tutorials, you'll quickly discover that Jahshaka is a very serious editing application with a learning curve that will keep you occupied for a while. Wide file-format support, node-based effects, and editing in DV, SD, HD, and film are only a few of the bonus features.
For home users with simple needs and conventional formats, I might recommend a Web-based app such as JumpCut, which was acquired by Yahoo last year. I find the editing features at JumpCut to be the best in its class, but I have also found that uploads have been getting slower of late.
If you test out or have already tried any of these apps, let me know what you think. And if you have any better suggestions for free video-editing software, please be sure to tell me about them in the comments.