Microsoft is investigating reported issues with Windows 7 and notebook battery life. The issue seems sporadic, but fairly widespread. It is unclear whether affected systems are simply misreporting the battery life, or if the battery capacity is actually being permanently affected.

Long before Windows 7 was released for general availability in October of 2009, users were reporting suspicious behavior with battery life, or at least reported battery life, when running the Windows 7 RC (release candidate) version. The Microsoft TechNet Forums thread on the matter dates back to June of 2009.

While some issues seem to be a simple matter of Windows 7 not reporting the remaining battery life correctly, or prematurely warning that the battery is nearly dead, there are users who have reported switching operating systems back to Windows Vista, or even a non-Windows operating system, and still experiencing drastically reduced battery life.

More: http://pcworld.com/businesscenter/blogs/bizfeed/188449/