While you can always access your emails, email id’s, etc from the Windows Live Mail, you may want to know the location of the folder where they are stored.
To identify its location, open Windows Live Mail > Tools > Options > Advanced > Maintenance > Store Folder.
If your Windows is installed on E drive, you will see it at E:\Users\username\AppData\Local\Microsoft\Windows Live Mail
Over a period of time, this folder may become large. So you may if you wish, also change the location of the Store folder here.