Image Upload Resizer

Hey all I was playing with the image uploader built into worpress in the write section of the admin. I was wanting to try and do something where my images i upload can be resized to my content width of 500px and then they can click on the image to view the larger one I uploaded. Is there an easy way to make the thumbnail radio button resize my images to a width of 500px instead of the 160px or whatever it currently does?