Depends how good you want it... I make snowboarding movies but it's just stuff shot with consumer-grade camcorders and headcams; if that's about right for you then:
Windows Movie Maker is just about workable. It's simple as fuck to use, but you'll soon reach its limits.
Adobe Premier Pro is fucking complicated at first, and many of the advanced features are really fiddly. This might well be a feature of all pro-level editing kit, though. It does have a metric shitload of options. You'll need to download a cracked copy or spend hundreds of quid on it.
Sony Vegas Movie Studio is forty quid, does most of the things Premier does, and does them easier. For me, it's the best fit.
That's the stuff I've used. Someone will probably be along shortly to tell me it's all a load easier on a Mac, and it's all bundled with it, and that Macs are much prettier and give you a bigger dick. They're probably right.