How to change the Windows 8 product key

Start the Command Promt in Administrator mode by pressing [WinLogo]+X,
then execute
slmgr.vbs -ipk ABCDE-VH26C-733KW-K6F98-J8CK4
To activate windows after changing the key:
slmgr.vbs -ato

How to fix broken packages

To fix broken packages in Ubuntu,

Go to System > Administration > Synaptic Package Manager and click Edit > Fix Broken Packages.
or in a terminal (Applications > Accessories > Terminal)
 
sudo apt-get -f install