I would recommed the latest version of Zwei-Stein, a free video editor from Thugs at Bay - http://www.thugsatbay.com/

I have used it in the past to edit video sequences for a new set of instructional videos. Don't let the fact that the programmers are German - there is an English version too.

It can have a slightly steep learning curve on some of the functions, but the time taken to learn it is worth the effort.