“Most people” running Windows 7 Build 6801 Prebeta will
soon realize they are running into trouble as the Windows Activation countdown nears 0. The Public Beta is scheduled for a December release and won’t give “most of us” enough time to use Windows 7 build 6801 before switching over. Luckily for you, the same way used to extend Windows Vista activation also works with Windows 7. You can use this up to 3 times. The maximum grace period will always be 30 days, so you’ll want to wait until you have 1-3 days left before using it.
1) Type cmd into the Start Menu Search
2) Right click the cmd icon and choose “Run as Administrator”
3) Type slmgr.vbs -rearm then press Enter
4) You will then be asked to reboot. After that, right click Computer, then select Properties. You’ll see that the counter has been reset to 30 days.
This only works 3 times and the counter never goes past 30 days, so make sure to wait until you have 1-3 days left before using it.