IE6 has an option for whether to shrink pics to fit the browser window. Let's see if I can find it. Tools->Internet Options->Advanced, scroll down to Multimedia. If you UNcheck "Enable automatic image resizing", IE will leave images at their original size. If you check that box, IE converts big images to shrunken, blurry bitmaps.
Once you've saved a large image, most image viewers (including the standard Windows image and fax viewer) will let you zoom in on the good parts. That's the main reason I like big images. Two other reasons are that if you ever want to print an image, you need about 200 or 300 pixels per inch, so to get a good 8.5 by 11 inch print, you need an image that's WAY bigger than screen size. And if you want to edit an image, like removing some zits, that's much easier to do with a high resolution image.