I.Open
www.windowsphone.com 2.Move over to the right and just below "search" you see your Live ID (and your current phone). Hover over your ID and a windows appears with all your phones listed.
3.Select the phone you are going to delete and that will be the phone that now appears UNDER your Live ID
4.Now click on Settings and a new screen appears where you will see on the left hand side just under the graphic of the phone the option to remove that phone.
5.Click it and the phone will be removed.
I have deleted phones from windowsphone.com before. I looked online and found the step by step instructions for you. Hope this helps.