Hope this works, I'd like to get this all figured out.
I found a great mouse icon I can't use... too big
- edy

If you have an image-editing program like Photoshop Elements (basically Photoshop light) or something similar you can open the file and resave it as a smaller size. Look in the edit menu of your image-editing program for a resize features.

They also list some online photo editing programs you can try at http://mashable.com/2007/07/23/online-media

Be sure to always use "save as" and give your new version a different name though so you don't overwrite your original.