If you are planning to get your hands dirty with the new Windows 7 Pre-beta build, beware that it will automatically expire after a trial period of 30 days.

Unless you attended the PDC 2008 and got an activation key, there is no method to activate Windows 7 forever yet but what we can do is extend the trial time period from 30 to 90 days which is way enough as we shall soon have Windows 7 Beta in our hands in almost less than 2 months.

This is the same hack used by most users to reset the activation expiry date twice in Windows Vista Pre-Beta and luckily it works for Windows 7 too.

Here is what you need to do.

1. Download Windows 7 Pre-beta and burn the ISO to a DVD.
2. Install Windows 7 Pre-beta using the DVD and while installation make sure to not put any activation key.
3. Once the installation is complete, open Command Prompt.
4. Type any of the following three commands.
sysprep /generalize or slmgr.vbs -rearm or rundll32 slc.dll,SLReArmWindows
5. Hit Enter
6. Reboot Windows 7 and enjoy another 30 days of free trial.

Note: This method only works twice so make sure to use it only when your 30 day trial period is about to expire.