This comes up every now and then when someone wants to attach some high resolution photos to a post and the Bulletin Board software won't accept the pic because it is too big....
You can go to http://www.faststone.org/FSViewerDownload.htm
and download this photo viewer that is really much, much more than a photo viewer. It allows you to resize photos to any size, even avatar size. It works with every photo format I have seen, and will even do a a batch convert of raw Nikon format into jpeg format. It's a pretty cool tool; it's free; no spyware; no junk mail -- and it also works better than any other photo viewer I have used. Only one shortcoming: It doesn't play well with Unicode filenames, such as in Russion, Chinese, Arabic, etc. And no, I don't get any royalties for this endorsement. I just like the product.