Modern cameras take photos with such large filesizes I think this problem is going to come up quite a lot now. A good free programme for resizing is Irfanview...
http://www.irfanview.com/Once downloaded, for avatars you just need to use it to view your photo, select 'Image' from the toolbar, then 'resize', then enter 80 pixels in the appropriate box, then save to your pc.
It's a handy programme to have as you can also crop, increase colour depth, sharpen, create borders etc.
