If your friends are still not sure whether they should get Vista or not, then you can tell them to use Vista as a trial and experience this great OS themselves. But the initial trial period is only 30 days, and for some, that’s not enough, so what can we do? Reinstall every 30 days until we’ve decided to get it? That’s probably not the best option unless you’ve got lots to spare time to kill. Here is a simple tutorial to show you how to extend Vista’s trial period to 120 days, which is probably more than enough for most of us 
Below is a screen shot of my friend’s Vista that has 4 days left on his trial period:
You only need to do a few things to extend Vista’s trial period (up to 120 days), so let’s see how easy its:
Step 1: Open up the Start Menu, click on All Programs, go to Accessories, then right click on Command Prompt and click on Run as administrator:
You should see a window that looks like:
Step 2: Now type in slmgr -rearm and hit the enter (or return) key on your keyboard. Then you should see:
Guess what? You have done it already! Just two easy steps 
Now let’s check the trial period of your Vista, but before we do that, lets restart your computer
After you have restarted your computer, open up the Start Menu, right click on Computer and click on Properties:
Take a look of the trial period…now it should be 30 days again
How do you get 120 days? Since you can use this method for four times in total, that will give you 30 * 4 = 120 days! But try not to do that because if you forgot to active your Vista on the last day…then you will enter the RFM (Reduced Functionality Mode)!!!
