What if 30 days isn’t enough time to make a decision whether pay extra to upgrade a copy of Windows Vista?
Just chill…
For those people who need more than just 30-days to evaluate their copy of Windows Vista, Microsoft has an interesting but rarely talked about feature to extend the trial license. Unlike other methods that freeze the activation countdown timer, extending the trial to 120 days requires no hacking, cracking or illegal third party files. All one needs to do is log into Windows Vista with administrator rights, launch the command prompt and type in:

slmgr –rearm

After a restart, the countdown timer will have reset to “43200 minute(s) (30 day(s).” Windows Vista will allow you to perform this operation a maximum of three times, so in theory, if one issues the “rearm” command on the last day of each trial period, a total of 120 days may be realized.