If you use Yahoo Mail as your email and found that when you click on a "mail to" link in Internet Explorer, a default Outlook Express or some other email program opens that you don't use or want.
So how do you get it to recognize your Yahoo account?
You just need to install Yahoo Messenger to get the correct plug in. Once you have installed Yahoo Messenger, you need to set your default email client to Yahoo! Mail in IE by going to Tools >> Internet Options >> Programs >> Email. (Vista is a bit more convoluted and I haven't tested whether this works)
Aftwerwards, go to Add/Remove Programs and uninstall Messenger if you don't want it on your computer. (Just don't uninstall Yahoo! Browser Services or Yahoo! Internet Mail.) Read on...