I was just looking at the timezone info, particularly timezone.inf. I think the info here: http://support.microsoft.com/kb/2779562 can be plugged into the file simply by deleting the '/' character and the extra space in the hex values. I'm curious too if the information such as "Starting in 2012, Bahia Standard Time will no longer have DST" could be used to remove unnecessary registry entries. Also, looking over older updates, it looks to me as though Egypt and Somoa may have inadvertently been skipped in previous unofficial timezone updates: http://support.microsoft.com/kb/2633952 http://support.microsoft.com/kb/2570791 I'm going to paste the text of what I've done for this so far. Note that I haven't attempted to use this to remove unnecessary entries. I understand this is relatively unimportant as you could simply shut off DST and manually change the clock if needed.