1) Open Internet Browser
2) Type %windir%\system32 into the browser address bar.
3) Find the file CMD.exe
4) Right-Click on CMD.exe and select 'Run as Administrator'
5) Type: net stop slsvc (it may ask you if you are sure, select yes)
6) Type: cd %windir%\ServiceProfiles\NetworkService\AppData\Roaming\Microsoft\SoftwareLicensing
7) Type: rename tokens.dat tokens.bar
8) Type: cd %windir%\system32
9) Type net start slsvc
10) Type: cscript slmgr.vbs -rilc (It may take a long time for this to complete, please be patient)
11) Reboot Twice
12) You may be required to Re-Activate. Use the Activate by Phone method outlined above
