Generally Kaspersky provide us 30 days trial period on its Anti-virus Product. So there are the few steps that you have to perform when your trial license going to expire after 30 days for getting a new trial license.
Step 1. Delete old key and turn off self defense (Settings-Options in kaspersky and turn off Enable self-defense, and click OK).
Step 2. Open Registry editor (click start in windows menu then goto run and write regedit and click Ok) and go through these :
For 32bit OS: HKEY_LOCAL_MACHINE \ SOFTWARE \ KasperskyLab \ protected \ AVP9 \ environment
For 64bit OS: HKEY_LOCAL_MACHINE \ SOFTWARE \ Wow6432Node \ KasperskyLab \ protected \ AVP9 \ environment
Step 3. Right look for PCID and right click and modify three or four last numbers or letters example : (8F10C22F-6EF6-4378-BAB1-34722F6D454)
and enter any other three-letter four-number and close the Registry Editor.
Step 4. Right click on Kaspersky icon in the task bar and choose exit.
Step 5. Go to Start-Programs menu, open the Kaspersky and when you activate searching trial license and you have new license of a peaceful month.
Step 6. Go to Kaspersky settings and turn on self-defense.
This is hardly a 2 minute job and you got again a trial period of 30 days, and there is no rush for more keys.
Note : Most of the patches that you will found on the net are basically work on that trick, they simply make the changes in the registry and change identification of your computer to the Kaspersky server, thus Kaspersky log server recognizes you as a new user and assigns you new trial license.