Under your account right click Start menu and select Explore All Users.
There will be folders under Documents and Settings for All Users, one for you and one for your wife. Under each account is a Desktop folder. Any icons in your Desktop folder appear on your desktop. Any icons in your wifes Desktop folder appear on your wifes desktop. Any icons in All USers Desktop folder appear on everyones desktop.
Move them as you see fit.
Also check All Users\Start Menu\Programs\Startup and see if the Incredimail icon is there. if so move to your wifes Startup folder.