Windows 7 product key must be enabled for use after 30 days. You can use the "rearm" command to extend your activation grace period. Note that the rearm command can only be used up to 3 times, extending your activation time to a maximum of 120 days.
1 Press ⊞ Win and enter "Cmd" in the search bar. The command prompt will appear in the search results.
2 Right-click the Command Prompt list and select "Run as Administrator". This will launch the command prompt application with administrator privileges.
3 Type "slmgr-rearm" into the command line and press ↵ Enter. A script will run and after a few minutes you will be prompted to restart your computer.
4 Restart your computer.
5 Check your activation status. Right-click "Computer" and select "Properties". This will open the System Properties window. Your activation time will be reset to 30 days.
Do not forget that this command can be used up to 3 times giving you a total of 120 days of potential activation time.