Hola, Real lake pls's trick
This is the key in the regedit to delete everytime you get finished of trial period,
don't delete each val, only press "del" key
by selecting " {BF4B9720-A035-11d4-9851-0080AD79471E} " in the left window of the editor.
you can search it also by pressing F3.
Path to the key :
[HKEY_LOCAL_MACHINE\SOFTWARE\CLASSES\CLSID\{BF4B9720-A035-11d4-9851-0080AD79471E}]