First open your email and scroll down to the picture you wish to save.
Step2
Right click the picture, and you should see an option that says "Save Picture As" if you click this it will open a "Save As" window so you can name the file and place to save it. (If you have outlook, your are done)
Step3
If you are using web based mail, you can right click the picture, and select copy.
Step4
Now open up Microsoft Paint (or any other photo editor software you may have) and click Edit, and then Paste as New Photo. Save this file, and you are done.
Tips & Warnings
Save files as .jpeg's to save space on your harddrive
If you save copyrighted pictures, remember you cannot post them elsewhere without permission.