Microsoft is working with its hardware partners to resolve a bug that causes some Windows 7-powered laptops to display incorrect battery warnings. Folks upgrading their laptops from Windows XP and Vista to 7 have complained that Windows 7 displays the following message: "Consider replacing your battery. There is a problem with your battery, so your computer might shut down suddenly."
It seems the alert isn't always right, though, and Microsoft says it's related to the way Windows 7 reads system firmware. The issue dates back several months, and many claim it began when they switched from the RC to RTM or retail editions of Windows 7. Along with the prompt, users say their battery life has been halved or worse, and at least one person purchased a new battery, but the issue remained.
Despite the bug, if you upgrade to Windows 7 and receive the warning it could still be legitimate, and Microsoft will help you determine if that's the case.