Not if you want to keep it as an image.. Well - Here I am, assuming you're on a Windows box (2000 or XP) - They lack the ability to resize an image.. If you're on a Mac or Linux box, they most likely have some sort of program installed..
But no, on a Windows box, if you want to keep the image an image, and not compressed into eg. a .ZIP file, which won't display, you'll need an external program as Gimp or the like...