windows does come with 'windows movie maker', a little on the basic side tho (it's in the start -> accessories folder.
or try the below programmes
download this,takes bit of getting used to tho -
http://virtualdub.sourceforge.net/
or this prog, it's called super and can convert virtual every known video file
http://www.erightsoft.com/S6Kg1.html
scroll to the bottom of the page to find the download link
both programmes are FREE
if need any help using either programme, let me know via email - neo@350z-uk.com