The are some additional tools avaliable for Windows XP and Vista, developed by Microsoft. To see them all, visit the MS Power Toys site. These tools were originally written for Windows XP, not all were ported over to Vista or Windows7.

The image resizer tool is worth installing ...

• The XP Image Resizer allows you to resize images in windows explorer by right clicking the mouse.
• The Vista/Windows7 Image Resizer clone of the above

With this tool installed, you can easily resize your images by hovering over your images and right clicking the mouse. This popup menu should appear...

You can select multiple images (with the shift or ctrl key) and do a big batch of photos in one go.

Medium (800x600) is usually the largest size we would use for websites. Don't forget, you have to think about the vistors internet speeds (not your own). If they have a slow internet connection, it will take longer for them to see your image, and they may give up and leave your site.