I'm confused, so I'm going to start at the beginning to make sure we're on the same page.
#1. When you say you 'went' to the website, I'm making the assumption that you read it and then clicked the link to the 'image resizer' to get here: http://www.microsoft.com/windowsxp/downloads/powertoys/xppowertoys.mspx
#2. You should then have scrolled down on that page to the 11th option on the right hand side...saying 'Image Resizer.exe' You click on that file and install it.
#3. Once the file has been installed, then you should have the option of right clicking any picture on your computer to resize it. Note: Your cursor must be 'on' the picture when you right-click to get the 'resize pictures' option.
If you did this, sorry about sounding like an idiot...but I have no other solution if that doesn't work.