I'm using Pinnacle Studio 8 - I mainly use it to capture from my camcorder and VCR to edit and it does a nice job. I don't know how good it is to use preexisting video, however.

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There's a thin line between genius and insanity - where's my eraser?

I use and recommend Vegas Video from Sonic Foundry (www.sonicfoundry.com). It'll mix and match just about any video format as input and output it as just about any format. It's extremely powerful, yet has a pretty clean interface (Windows only, though). While you still have to render the video when you're done editing, you get real-time previews of effects while you're editing. It's not cheap, though if you're a student or know one then you can get an academic discount.

Also, they sell an entry level version called Video Factory that's much cheaper, but I'm not sure that it'll handle all the different formats.

hth

you can find many video editing software here.