you can't. the tool that comes with windows for editing video is "windows movie maker". this is found under start-->programs-->accessories in windows XP. i don't know where it is in vista, i don't use vista. there are also many other open-source or freeware video editing tools if you don't like WMM. Google "edit video freeware" or "edit video"+"open source".
since you asked this question in PDAs and handhelds, it seems that you want to do this editing on your phone or PDA. there are no programs that will edit video on a handheld. you must move the video to your computer.
