How to make the mailto: protocol work with the gmail tool instead of Outlook
Contributed by TallGuy 
November 11, 2004 
Tagged: Windows
If you downloaded the Gmail Notifier tool, you might have noticed the ability to make Gmail your “default client.” It doesnt work if you have outlook installed though, and it isn’t on the menu in IE. Here’s how to fix it!
Go to Folder options (View>Folder options on 98/ME \ Tools>Folder Options on XP/2003)
Find the thing thats like URL Mailto (it has the outlook logo)
Click advanced and delete anything there
Hit ok and then go to the gmail options (on the task bar)
Uncheck the box about the mailto thing
Repeat, thus checking it this time
And it works, amazing.