Gateway Computer

I'm helping a friend with her Gateway computer running Windows 8, she can't remember her password to get into Windows, which is the same password for her windows account. Windows sent her password to her e-mail address, but alas she doesn't know the password to access her e-mail from another computer, and Yahoo has been no help. Does Gateway install the OS on a partition on the hard-drive, it looks I am going to have reinstall Windows to access this computer, will she need the Windows activation key, which she doesn't know where it is, if I reinstall Windows? And is Windows 8 on a partition that I can access via the Bios?