Whenever I email pictures to someone, Windows XP asks whether I want to shrink them or keep them the same size. But I can’t for the life of me figure out how to make smaller versions of the files for myself, other than the time-consuming and clunky method of emailing them to myself and then saving the attached files.
Any ideas?
Are you looking to reduce the file size or the physical size?
File size.
I use Image resizer from Windows XP Power tools .
Damn, I could show you in 2 seconds in Photoshop. 
If you have any image editing programs at your disposal let me know.
Basically you want to reduce the resolution, but you can also reduce filesize if you reduce physical size. So if the thing is 20 inches by 20 inches size it down a few notches.
You can also save as a JPG which is a compressed file.
I second Daizy’s Windows XP power tool suggestion.
It puts an option in your right-click mouse menu to resize image files, and you can highlight a whole bunch of files and resize them all at once, without ever opening up a graphics program.
I use it all the time when I email digitial pics that I don’t need to retouch or edit.
Any of many image manipulating software suites will do what you want. I use Corel DRAW and PhotoPaint.
I don’t use XP, but for years I’ve used WinZip and LHARC to shrink files for emailing.
When you change an image’s measurements, say from 1024x768 pixels down to 640x480, that’s called resizing. When you wish to reduce an image’s file size, say from 750 kb down to 50 kb, that process is called optimizing.
Both can be used to manipulate an image, based upon specific needs.
A quality graphics tool can optimize an image. Photoshop, Paint Shop Pro, PhotoImpact can all do it. You can download 30-day trials of the latter two and have fun.
Fast, easy, good quality and the perfect price. 
Use SnagIt. This is an awesome little program that can take screen captures, convert between different file types, do scaling, etc…