If you do not mind a steep learning curve, and want excellent results, go with Adobe Premiere 6.5, or latest version is Pro/7.0. You need a fast machine with lots of RAM and hard drive as there is lots of data to be processed. I have 6.5 and am always impressed with both its quality results, flexibility, and complexity to do even the simplest things.
If you want something easier to learn with excellent results, go with Pinnacle Studio v8, otherwise simple edits can be done with MS MovieMaker that comes with XP.