Vidding software

[beatrice_otter]

I would like to do some very, very basic video editing--I'll be making basic informational videos to upload to youtube, and I don't think I'll need any of the bells and whistles needed to do, say, fanvids, but that may change as I get into it.  I need to be able to compress video, and I need to be able to add pictures to a video.  I would prefer a free or inexpensive program, but I don't know enough to evaluate the differences between them.  Googling is pulling up lots of possibilities, but again, I have no idea how to make an informed decision.

My OS is Windows 7.

What do you recommend?  What should I be looking for?
Help!