Toshiba RTS Problem

I was readying an old Toshiba notebook computer for re-use after several years of dormancy. As it booted, it complained of an RTS problem.

At first I thought the backup battery needing replacing. (All computers use a small battery to retain settings when the computer is off.) 

After some research, I found that it merely needs recharging, like this:

1. Fully charge the computer's battery (battery charge light turns green).

2. Turn on the computer, and then start Windows.

3. Leave the computer on for at least 6 hours.

This forces the computer to recharge the RTS battery, and the error message goes away.