Two points:
1. Windows Live Mail does *not* come with Windows 7. No e-mail program
comes with Windows 7. It's a free Microsoft program that can be
downloaded and installed on any recent version of Windows. If it came
with your Windows 7 computer, it's because the computer's manufacturer
elected to install it, not because Windows 7 came with it.
2. You can normally uninstall it just as you would any other
program--Control Panel | Programs and Features. But if it came
preinstalled on your computer, it might be somewhat different; I'm not
sure.