slmgr -rearm
HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/Windows NT/CurrentVersion/SoftwareProtectionPlatform
–>“SkipRearm”=dword:00000000
Just change 00000000 to 00000001. (After 3 Rearms Windows 7 Reaarm key would change to 00000000,So we have to change the value to enable Rearm once again).