If wanting to add a completely new time zone to Windows Vista where it is not already on the drop down list when clicking "change time zone", I found this way to be successful:
 
1. Download the TZEDIT.EXE file (clicking "allow" wherever permissions are required).

2. right click TZEDIT.EXE and run it as an administrator

3. click "allow" when required

4. In TZEDIt, click the "NEW" button and then create the time zone (GMT+/- HH:MM) name of location/place e.g. (GMT+11:30) Norfolk Island

5. click on the hours numbers in the clock and move it up or down (+ or - GMT) as needed and then do the same for the minutes (usally half hour changes in most places where Microsoft has not included a specific place or timezone)

6. add any dayliht savings changes if any apply to the place/location being added as a new time zone (none aply to Norfolk Island)

7. In the mandatory entry block, delete the asterisks and words mandatory entry and insert the name of the time zone e.g. "Norfolk Island Standard Time"

8. Click "OK" when done in the new entry box for TZEdit and then click "Close to close TZEDIT.

9. This will leave you with a registry key which shows a time zone entry for Norfolk Island in MS Outlook but not in the system clock list

10. To have the system clock list showw the new time zone, it is necessary to go into RegEdit and follow the HK Loca machine\Microsoft\WindowsNT\time zone branches until the list of time zones can be seen

11. It s then necessary to click on the new timezone registry key in the left window of RegEdit that you have created

12. It will be seen in the right window pane that compared to the other time zone registry keys, the new time zone is missing an "Std" string value file. This file needs to be created for the system clock t see the new time zone.

13. while staying clicked on the new time zone entry in the left window pane, In the "Edit" command at the top of the RegEdit box, click "Edit", then "new", then "string value" and you will gt a popup box askign you to name the string value - name it "Std" (be sure and remember the "s" is a capital) and then close the pop up box

14. You will now have a new registration file called Std in the right window pane

15. Click on the word "Std" in the list of files in the right window pane of RegEdit and a popup will show a list of options, click on "Modify" at the top of that list

16. a popup will appear showing the word Std at the top field and allowing you to enter words in the second field

17. type the name of the time zone e.g. "Norfolk Island Standard Time"

18. close that popup and then the name of the time zone should appear on the right hand side of the file type with the file name "Std" on the left side of the file type

19. Exit Regedit once the Std file shows that zone name

20. Go to the date/time settings didgial clock at the bottom right hand of the Vista desktop and click to change the date time settings

21 click "change time zones" and the system clock drop down list should now show the extra or new time zone you have created

22. click on that new time zone and your system time should now change to that new time zone

23. It is now possible to activate the internet time synchronisation to keep your Vista computer accurate in the new time zone

24. One of these days, Microsoft may be able to add a "add non-listed time zone" button which carries out the steps referred to above

25. The problem seems to be that TZEDIT works well in Windows XP etc but Vista needs the addition of the Std string value file in the registry key for the new time zone before it will be recognised by the system clock time zone list

This was done on Vita Home Premium on a Toshiba laptop linked to an office network and it finally worked after many frustrating hours.

Hope this helps other Vista owners seeking to add a time zone not in the standard MS Time Zone list for Vista.

As usual, no liability accepted for any loss or damage etc whatsoever if anyone uses RegEdit and wrecks their computer for any reason.

This is intended simply to help others figure out a solution to the problem

PS: I got sick of clicking on website after website in Live Search, Google, yahoo etc for time zones and Vista to only be told how to change time zones within the factory loaded time zone list and no answer on how to add a new non-listed time zone.

I am sure you all know the feeling.