"The wireless mouse battery level is critically low. Replace the batteries soon so the wireless mouse will continue to function properly."
Here is a copy of what it looks like on my screen:
My problem is it's 12:30am, and I really do not feel like running out to the store to buy some AAA batteries. So, it's just going to have to wait. Also, I would love to have Microsoft define "Function Properly", as I don't think any of there products meet this yet.