Since I use a lot of virtual computers for labs at my college, I have used this trick to extend the activation time for windows 7. It does work for vista if you need it.
Extend Windows Vista and 7 Trial Period from 30 Days to 120 Days
You have to use the same slmgr -rearm command in this method too.
So here is the step-by-step method:
1. Click on “Start button -> All Programs -> Accessories“. Right-click on “Command Prompt” and select “Run As Administrator“. If you are prompted to enter password, enter the password and continue. You can also open Command Prompt in Administrator mode by typing “cmd” in Startmenu Search box and press “Ctrl+Shift+Enter“.
2. Now provide following command:
slmgr -rearm
3. You'll be prompted to restart Windows, restart it and the trial period will be reset to 30 days again.
4. You can use the same command 3 times. In this way you'll be able to use Windows for 120 days without activation.
5. Now its time for the main trick. Type regedit in RUN dialog box and press Enter. Now go to:
For Windows Vista:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\ SL
For Windows 7:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SoftwareProtectionPlatform
6. In right-side pane, change value of SkipRearm to 1.
7. Now you'll be able to use the slmgr -rearm command 8 more times. So you'll get total 360 days for using Vista and 7 without activation:
120 days by using slmgr -rearm command before registry editing
+
240 days after registry editing
||
360 days