First I'll tell you what file is in charge of this hack. It's called slmgr.vbs which lives in the C:\Windows\System32 directory, as you may had noticed this is a vb script. The way to activate this hack is pretty simple.
1) Open an elevated-command prompt (CMD with Administrator privileges) RUN=>CMD
2) type in the following and then press enter...
slmgr -rearm
#Now you should see a confirmation dialog that says "Command completed successfully. Please restart the system for the changes to take effect." As indicated restart your OS and now your activation period should of been extended to 120 days.
3) To check your currently activation period type in the following and then press enter.
slmgr -xpr
#A dialog should appear telling you how much you need to wait before activated, however, if your OS is already activated then the dialog should say that the OS is activated permanently.
Done!
Some other options to this command
slmgr
-ipk
-ato Activates Windows
-upk Uninstalls the current product key
-xpr Displays expiration date of your Windows OS license
-dli Displays basic license info
-dlv Displays detailed license info
-flopex