Another thing that can get in the way of successfully getting an 80x80 avatar is Exif data that can come along for the ride. Digital cameras often add yards of this data. Exif data includes items like what lens was used, the f-stop, distance to the subject. This extra data bloats the size of the result.

When that is the case, you want to use image software that gives the option of not including the exif data when you save the file.

I've used Irfanview for years and it's freeware.