Machete Lite is a simple video editor which makes it easy to trim surplus content from AVI and WMV videos. And it does so without re-encoding them, so you can remove an unwanted intro from a clip and save the enhanced results, without any loss in quality.
The program is extremely basic, but this does at least make it very easy to use. Open a video and you can play it as normal; you're able to step through, frame by frame if necessary, to find the footage you need (or, perhaps, don't need); select the beginning and end of the section you'd like to trim, and you can then delete it at a click.
There are multiple ways to carry out most actions, which again helps to improve usability. So to step through your video, for instance, you can drag a slider, click a toolbar button, choose a menu option, press the left or right arrow keys, or use dedicated keyboard shortcuts.
And although the program is really just about trimming unwanted frames, there are one or two small extras on offer here. So a Tag Editor helps you to edit the file's metadata, for instance; you can save the current selection as a separate video, or just save the current frame as an image (though only in BMP format).
Please note, the authors also produce a more powerful commercial version of Machete. This supports many more formats (MP4, MOV, FLV and so on), can extract the audio stream from a movie or replace it with another file, and includes a few other capabilities. It's yours for $19.95 and you can find out more at the Machete site.
It's extremely basic, but if you're just looking for a way to trim your AVI/ WMV videos then Machete is a quick and easy way to get the job done.