Follow the steps to change signature in Windows Live Mail account:
• Click ‘Windows Live Mail’ button.
• Choose Option | Mail from the menu that appears.
• Go to ‘Signatures’ tab.
• Ensure that ‘Add signature to all outgoing messages’ option is selected.
• Also deselect ‘Don’t add signatures to Replies and Forwards.’
• Now edit the signature that you already see in the signature message box.
• Click ‘OK.’
If things don’t work out the way you want, contact Windows Live Mail Support Number.