This is sorta complicated.

I have a video that's about 1 hr 20 minutes long on a macbook pro. I want to compress it into a format that a PC will read and that Microsoft Movie Maker can edit. So .avi right?

Can anyone suggest settings to retain "best quality" and still keep the file size manageable. I'd like to keep the file size smaller than 4.7gb, so that I can xfer from macbook to a PC easier than hooking up thru my unstable network. I suppose if we have to - I can break up the clips to keep the file sizes smaller.

Any tips? I am Mac Stupid.

.avi is just a container, much like quicktime is just a container.

It all comes down to Codecs - you need to see what Codecs the software on the PC supports and then transcode it, if required.

iMove will save some file types, and QuickTime Pro will also let you transcode. If you google around (I don't have time right now or I would) you can also find some free programs to convert between different codecs - say MPEG2 to MPEG4