Sorry but I haven't used Windows 7 or Live Mail for years, so all I can do is search for answers for your problem.  Here is what i found first.

Please follow the steps below on how to repair Windows Live Mail:

1. Go to Control Panel.

2. Under Programs, click Uninstall a Program.

3. Locate Windows Live Essential then click Uninstall/Change.

4. When a window appears, select Repair all Windows Live programs.

5. Restart your computer after the repair.

You can also follow the steps below:

1. In the folder pane, locate C:\Program Files\Windows Live\Installer there is a repair utility. 
2. Run wlarp.exe file.
3. Click Repair all Windows Live program.
4. Follow the on-screen instructions to repair Windows Live program.


That came from here.

https://answers.microsoft.com/en-us/windowslive/forum/all/repairing-windows-live-mail/5e582832-3623-4259-a2cb-3b1e71a18cc6?auth=1