Putting together mixed format into iMovie HD6, need help

I started a movie in the 4:3 ratio (is aspect the right word?) a while ago, and now am adding some interviews done by someone else, which were sent to me over the internet. Nice pictures,about 11 short interviews, but 3 of them are done sideways. Cameraman must've turned the camera sideways to take the movie. Is there a way to fix this?

Also, some material I am trying to add to the movie, is done in 16:9 ratio, and I am getting the black bars across the top and bottom, and some are boxed in. How can I make the all the same with out the letterbox thing.? From here on, I will use 16:9, but there is too much in this movie to start over. I am not a professional, anything but, however, I make cute movies. :-)

The movies clips I downloaded are full size when I open the files, but have the black bars when inserted into the movie.

I am using a refurbished MacBook Pro , 10.7.5, with iMovie 6. Thanks for any help. Marjorie.

P.S. another problem - the audio cracks up in certain places, and yet when I play it over, it may play fine. I will be putting this into DVD format to burn to a disk.. Do you thing the audio will copy OK? Is there a way to correct this.

AlsoI am getting error messages from Apple, sometimes, when I save my work. and it shuts down automatically, but does not seem to bother the content???.