You will find that if you try to make an Avatar within your profile that you will not be able to use a normal sized picture.
Use the progaramme link below, you will be surprised how easy it is
You will need to re-size your picture so that its width does not exceed 150 pixels, the height cannot exceed 200 pixels, and the file size cannot be higher than 64 KB. ( but hey no worries thats what the links for)
A quick easy way to do it is to pop a picture that you want to use on to you desktop and then direct the above programme at it, or download a picture to your desktop from the net and do the same.