I have a music system using XP and another with Win7, neither require login. Unless you and wife need different starting screeens, you could easily share. The benefit of having separate logins if there are multiple users is that her documents will be automatically stored in her folders (my documents, my pictures, my videos, etc) and yours will be in yours. If this feature is not needed you can share and have windows just launch to the startup screen right away. If there is only one profile (and no password) in the User Profile area of control panel, windows will just launch to the full start screen.

You can also have separate logins without needing to 'sign in' with a password. Just make the password empty in the User Profile area and then when Windows launches you just click on which user you want to be and it will launch windows right away with your preferences, desktop setup, and profile folders ready to go.

I do not work here, but the benefits are still awesome
Make your sound your own!