I wonder if anybody else has had this occur . . . when I bought my computer about three years ago, my computer clock showed all the global time zones to choose from for my settings. Now it only shows the west coast of California, into Mexico and South America (presumably; where is Baku?) I live on the east coast, USA, and now I can't set my clock to automatically adjust itself; it shows my time as one or several hours off from my local time. I'm guessing that some update or other has done this, but I haven't seen anything on the Microsoft or other websites that address any glitches or issues with this problem.

This seems to imply that tthe INTERNAL battery of your PC is going out of power , this is a small manipulation requiring a little care ; any PC store will telle you how to do that ; the lifetime of the internal battery is about 3 years but maybe less ; if that is not the answer you might have a problem with your motherboard .

Thanks for your reply, TCHAPIEV. If it is the internal battery, would that manifest other problems I may have noticed? Or does it only control clock settings? Same question for the mother board . . . could the motherboard have a problem that would only involve the clock?

In other words, if it is either of these, is there typically another symptom that would be a tip-off that something is wrong?

   If your battery is low, your computer will not keep time properly when it is unplugged.  That does not seem to be what you are describing.  You are saying that not all of the time zones are showing in the Time Zone map.  Is this correct?  I have never heard of that and I would not think that a dead or weak battery would cause that.
   Try double clicking on the time at the bottom right of your screen.  When the Date and Time Properties box comes up, go to the Time Zone tab.  Click on the drop down box at the top and try to find the GMT-05:00 time zone.  One of the GMT-05:00 items should be called Eastern Time but if not any of them will be your time zone (I am assuming that you are in the Eastern Time Zone).
   What happens when you do that?

Sorry, I was referring to that drop-down box in my original post . . . it only shows the time zones mentioned above. It USED to show all of them when I first got the computer.  Now just the few I mentioned.

I noticed that my clock kept changing itself, so I went into the menu and could no longer find my time zone. I had to set it to NOT automatically link to the global clock to correct itself for Daylight Savings Time, etc. because it would set my clock one to a few hours off.

Wait  . . . Time Zone map?? I've never seen a map, only the drop-down list. I'm using Windows XP, does that matter?

Maybe I'm a dope or something, but I know it had Eastern Time in the menu to begin with!!

   Please double click on the time at the bottom right of your screen.  When the Date and Time Properties box comes up, go to the Time Zone tab.  Click on the drop down box at the top and try to find the GMT-05:00 time zone.  You may have to scroll up or down.  I think that you just did not scroll up or down.  I have never heard of it not all being there.  If it is not all there, reinstalling Windows should fix it.

Yes - the Time Zone tab only shows 10 regions:

GMT -08:00 Tijuana, Baja, California
GMT -07:00 Chihuahua, LaPaz, Mazlatan-New
GMT -06:00 Guadalahara, Mexico City, Monterey-New
GMT -04:00 Manaus
GMT -03:00 Montevideo
GMT +02:00 Amman
GMT +02:00 Beirut
GMT +02:00 Windhoek
GMT +03:00 Tbilisi
GMT +04:00 Baku

These are all it shows. There is no scrollbar to scroll up or down. Also, if I click on the Internet Time tab and check the box to automatically synchronize with any of the links, I get a message that an error occurred while Windows was synchronizing.

If I reinstall Windows, do I have to completely uninstall it first?

Thanks so much for your responses, this has had me befuddled. I've thought that maybe someone in those regions has pirated my computer . . . but then the clock would still show all time zones . . .

   I did a little more research and it seems that those are kept in the registry.  So it sounds like what happened is that those items in the registry were removed somehow on your computer.
   Reinstalling Windows should put the missing ones in (and, no, you do not need to uninstall Windows first) but here is an easier way.  Hopefully, this will work.
   I exported my time zone entries from the registry and put them at http://regvac.com/timezones.reg.  When you click on this link, it should ask you if you want to Run or Open it.  Choose Run and that should put those entries in the registry.  Hopefully, that will fix your problem (if it does not seem to work initially, try restarting Windows and then seeing if it works).  Let us know if that works.

It works! I loaded your entries, rebooted, and now it shows the map and all the time zones. I was able to synchronize with time.windows.com, but it set my clock forward three hours (yes, I chose the correct time zone ). So I corrected the time, tried again, and it set it within a minute of my time. Most bizarre. But anyway, that fixed it, THANK YOU so much for your help! It's a minor issue, but I keep my computer clean, and this really bugged me.