You question isn't "dumbo" if you don't know the answer.
You stated you don't want to use any software, but unfortunately you will have to in order to change the hotkey so it will open up to yahoo mail.
Go to the following page, make your selections.http://www.microsoft.com/hardware/download...spx?category=MK
If there is download for your keyboard, download it, then install.
After installation, open up the program.
You should see a Key Settings tab.
Click that tab.
You'll see a list, choose the email key name, highlight it.
Next click on Configure, change, or something similar.
Do you see Custom? If so, choose the setting to Start program, web page, file (you may see something similar if not the exact thing I listed)
Click NEXT, enter the path in the box. In your case it would be the url for yahoo mail.
Try the email key to see if yahoo opens up.
edited to include link
Edited by Queen-Evie, 25 March 2009 - 04:04 PM.