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.

The -rearm command resets the licensing status of the machine. To check the current license status of said machine, the -dli or -dlv parameters will yield something similar to the following:

C:\Users\Majesty>slmgr -dli
Name: Windows(TM) Vista, Ultimate edition
Description: Windows Operating System - Vista, RETAIL channel
Partial Product Key: XXXXX
License Status: Initial grace period
Time remaining: 43160 minute(s) (29 day(s)

Is Microsoft's "rearm" command a forgotten relic from the beta trial period or working as intended?  Microsoft could not be reached for comment with regard to the issue, but as of now, it looks like extended grace periods are the status quo.