Want folder sizes to be displayed in the explorer view on Windows XP?

It's a little application called Folder Size and it is designed to show folder size and children. It works only in Windows XP and is available over at Folder Size

It's a brilliant little idea, and doesn't add any noticeable lag on the system at all.  The instructions on the site should be able to help you get it set up with no problem, and once you have it, I don't think you'll be going without it again.