Below is how to do what you want using Chrome and Gmail. It should be fairly evident how to adapt the method to work with IE8 and hotmail.
Make mailto: links open in gmail in Google Chrome browser (Windows XP & Vista)
In any windows explorer window (except desktop):
This should all be on one line with a space between the quotation mark
after the path info and the https. My path was
C:\Documents and Settings\Brendan\Local Settings\Application Data\Google\Chrome\Application\chrome.exe
To find yours, just right
click on a google Chrome shortcut (like the one in your start menu),
go to “properties” and copy the “Target” field.
In Vista, your path will be something like
with “Brendan” being your username.