Hmm, if you download
ACDSee 32 (the one released for free, and the best overall image viewer on PC), you can use it to resize images. Photoshop or Paint Shop Pro can also do it, but they're not free...
The problem when resizing images is how to handle the size increase/decrease. A web browser would only cut away or add pixels, thus not making a very good end product. The other graphics handlers have other methods, which are smother but somewhat blurrier. ACDSee has a pretty good resizing method, but Photoshop and Paint Shop Pro have the best. (Together with many other graphics editing programs)