#1) Open CMD (as admin)(Press Win key and X and select Command Prompt (Admin) )
#2) Run these commands -one line after the other- by replacing <KMS KEY> and <KMS SERVER> with a KMS Key/Server from the links below:

slmgr.vbs -ipk <KMS KEY>
slmgr -skms <KMS SERVER>
slmgr.vbs -ato

#3) Tarraaa!! Have Fun 


 
KMS SERVER LIST (UPDATED) (You can check the statuses of the servers here.):
 
Windows and Server + Office 2010/2013:
whwebsolution.no-ip.org
kms.shmtu.edu.cn
kmsme.no-ip.org
jbiz1.mooo.com
walkercorps.zapto.org
 
Windows:
whwebsolution.no-ip.org:80
fourdeltaone.net
kmsforwin8.xicp.net
win8kms4.mooo.com