K5 video postprocessing software (video newbie questions)

Since you are new to editing and looking for something free why don't you give Windows Movie Maker a try. It's pretty simple and user friendly. Since you have a PC it should already have it on there but if not you can search it online and download for free. Obviously it doesn't have all the advanced controls as some of the programs other folks mentioned but it would be a good start for you. I started out using Windows Movie Maker and now also use Sony Vegas Movie Studio HD Platinum 10 and Pinnacle Studio 15. Good luck!
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Jeremy