I’ve been trying to achieve this for a while now: http://computernetworkingnotes.com/xp-tips-and-trick/remove-administrator-password-password. However i am running windows 8, and i’m not sure this would work. Can i use Ubuntu to fix this? Yes, you can use Ubuntu. You need to install chntpw, in a terminal type: apt-get install chnpw. Then mount your windows partition (usually it will auto mount if you are in a file manager)”]
Source: https://askubuntu.com/questions/389757/removing-windows-8-syskey-encryption-password