Save your old avater pic, say on your desktop or somewere. Than go to user contol panal (upper left) edit prfile, than edit avatar or add . Just make sure your size and PX count is what is required. Hope this helps and if not let us me know whats hanging you up. Trust me I went through about 40 minutes of pain once i figured it out I realized it should have only taken me about two minutes. 38 minutes was my bad.
If anyone is having a problem getting it to work, I am guessing that you could e-mail the image that you are wishing to downsize and use to someone that has done it, and maybe we could resize the image for you, e-mail the smaller image back to you, then you could resave the image and post it to this NEW FORUM.