andy this one is not compatable with anybody with windows vista .I use a similar thing from microsoft. http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx
About half way down on the right hand side you will find "image resizer". Download this.
Next, go to the picture you wish to use, right click it and in the list of options (near the top of mine) is "resize". Click on that and then choose which size you want to make the picture.
Rather than changing the orginal picture, it makes a copy of it in a smaller size. This way, your orignal is left "unharmed" by the experience.
Hope this has been of some help to you