How to tell what Microsoft Time Zone Update you have

Windows XP, Vista and Windows 7 …
Have a registry value you can check to see if a Time Zone update has been applied.
Under the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones registry key.
For Windows 7 and Vista, this is the TzVersion key.
Windows XP, it’s the KBLast key.
Windows 2000, is a mystery to me.

Windows 7
For the September 2010 Time Zone Update, the TzVersion key is set to 131728128.

Windows Vista
For the September 2010 Time Zone Update, the TzVersion key is set to 131728128.
The lack of a TzVersion key means that you don’t have a Time Zone update applied.

Windows XP
For the September 2010 Time Zone Update, the KBLast key is set to 131728128.

In the screenshot above, the KBLast key is set to 955839 . Since that update (December 2008), it looks like Microsoft have changed the versioning scheme.

Windows 2000
?

Further reading:
How to configure daylight saving time for Microsoft Windows operating systems
September 2010 cumulative time zone update for Windows operating systems

Update 1st October:
Added Windows Vista details.

How to tell what Microsoft Time Zone Update you have

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