My default mail client is not set on my computer. How do I set up my mail client again so this doesn't happen?

Full Question: My default mail client is not set on my computer because of a program I tried using. Every time I click an email link on a webpage, it doesn't know what to do. How do I set up my mail client again so this doesn't happen?

This should do the trick. If you navigate to your Internet Options in Internet Explorer (if you have it), there is a tab for Programs. These are your default programs to be used when you click links for emails and other.

If this doesn't help, let me know. This should work for Firefox as well.