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)
WIndows XP
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.
Windows Vista
In Vista, your path will be something like
C:\Users\Brendan\AppData\Local\Google\Chrome\Application\chrome.exe
with “Brendan” being your username.