
The basic way this works is that at the end of the 30 days, you’ll need to run a small command and reboot your computer, at which point you’ll have 30 more days, up to a maximum of 120 days. This trick should work regardless of where you got your copy of Windows 7 from.
Extending the Trial By 30 Days :
The first thing you’ll want to do is check how many days are left in your trial period. You can do this by right-clicking Computer and choosing Properties…
At the bottom of this window you’ll see how many days are left to activate (19 in my case since I installed this box ).

Windows 7 Command Prompt as Administrator

Next you’ll simply type in this command:
slmgr -rearm

Within a few seconds you’ll normally see this dialog show up, saying that the command has completed successfully, at which point you’ll want to reboot. Windows 7 slmgr Success
Checking the system properties again shows that I now have 30 days left to activate.
Windows 7 Activation 30 days .you can do this process 3 or 4 times...

If you are any quire's please contact me
THANK YOU......