Hi

My laptop is loaded with Windows 7 Ultimate recently.  Since then the battery is not charging. Earlier to that in Windows XP professional the battery was functioning properly. I read from forum that if I go for BIOS upgrade it could resolve. I am not confident about BIOS update. As i am not aware is revert to (current) BIOS is possible at software level 

Also, Is a firmware update/upgrade require re-install of Operating System?