what does the other look like? a picture might be good here.

The other icon is a white 8.5x11-proportioned and portrait-oriented rectangle with three too-small-to-distinguish round images horizontal on the page. The three images are colored. One is blue, one red the other green (I think). I will try to capture a screen shot tomorrow when I am using my other computer. On this computer the TB icon is the blue bird.

Thatc sounds like the windows icon cache is corrupt. The icon cache is located at the hidden system folder location below:

C:\Users\User-Name\AppData\Local\IconCache.db

type %appdata% at the search in the start menu and press enter open the local folder in explorer delete iconcache.db

Now it is a very long time since I have done this, but I think I recall a reboot being required. But a really do not remember.

Here is a screen shot of my Task Bar showing the two Mozilla icons. As you can see, the Firefox icon is the traditional fox, but the TB icon is not the usual blue bird with the envelope. You suggested deleting something called iconcache.db, but how will I get back my windows icons? More confusing to me is how the Windows icon cache can have anything to do with Mozilla icons. I have not noticed any other icons that seem unusual or not as expected.

Well, the task bar and the icons are managed by Windows, not Mozilla.

Hi Zenos. Thanks for chiming in. You say that Windows manages icons in the task bar not Mozilla. Ok. Well how does Microsoft know years in advance what icons program manufacturers like Mozilla are going to be using? I am skeptical. So, do you agree with Matt in advising me to delete all Windows icons? Scares me frankly. Did you look at my screen shot? Firefox icon is correct. If I delete Windows icons, will Mozilla icons also be deleted? What about icons from other manufacturers? How will I get all my icons back again?

It's a cache. A quick-access all-in-one-place location for frequently used icons. It saves the system having to visit each application and locate its icon just to populate the task bar and menus.

If the cache is found to be absent it'll be automatically rebuilt. Fear not.

Matt and Zenos: Your recommendation did not work. I deleted iconcache.db and rebooted the computer. The iconcache file which had been approx 6500KB reappeared as approx 2500KB. The Firefox icon continues to display correctly but the TB icon is still not the blue bird carrying the envelope. The TB icon on the exe file in the program folder, the icon on the start menu, and the icon on the task bar are all the same.

My theory is that, to paraphrase President Obama, if you like your blue bird icon, you can keep your bluebird icon. Seriously, possibly people upgrading from earlier versions can keep the bluebird icon, but new installations of TB starting with version 31 no longer include the bluebird icon.

I still have the blue bird icon on my two linux computers, on my windows 7 computer and it's there on my partner's windows 8 computer. It sounds like Matt has his too, so we come back to what's wrong with your computer?

Right! What indeed is wrong with my new computer that I got last week? Seriously, I bet yours and Matt's and your partner's computers all have updated versions of TB. Mine is a completely new install. No preexisting icon. My thought that Mozilla did away with the blue bird starting with version 31 could be a possibility. What else could account for it?

Where are all the other new installers complaining about the icon?

Point taken Zenos. My idea was (partly) in jest. Just racking my brain. Any other thoughts on how to approach the problem? What about the fact that the iconcache came back at less that half the size of the deleted version. What do you suppose that means? Another thought - is there any way to associate specific icons with specific programs similar to the way file types can be associated with specific programs to open them?

And the thunderbird-31.3.0.tar.bz2 installer for Linux contains these icons, below.

Sorry, I can't help with questions about the Windows environment, as it's all Linux here at home, and I'm rusty on the ins and outs of Windows. I have vague recollections of there being an option or tool to rebuild icons for the desktop environment, but that would date back to XP or maybe Windows 2000.

Matt?

Thank you Zenos. I really appreciate your trying to help me. I am hoping that perhaps Matt will chime in with a new idea.

here is some of that scary windows stuff...

http://www.thewindowsclub.com/rebuild-the-icon-cache-windows :-p

This next one appears to be trying to sell a utility program, but I think you can go through to the last bit where you type into the command console:

http://www.winability.com/how-to-erase-icon-thumbnail-cache-windows-8/

That Icon is a generic windows one. Lives in shell32.dll if I remember my Windows correctly.

The cache is just that. Each executable or file has an icon associated with it, which is extracted from the relevant Executable or Dynamic link library at the time the shortcut is made and added to the icon cache.db so windows is not opening 200 files to get icons when it starts. It is also particularly prone to corruption, or certainly used to be. The internet is jam packed full of tutorials on how to rebuild the icon cache as a result. Like most caches, when you stop using an icon, it is not removed, just ignored so it grows over time. I am sure you have heard people say Windows slows down over time. This is one of the factors in that. Registry bloat is a far more important one, but draws from the same principal, things not being actually removed.

What is happening here is a little more insane really. I do not know the cause only the outcome, which is as you describe. If you have one in iconcache you can keep it, were the other complaints are I do not know, but it may be they just think it was changed. The following should fix the icon.

Right click the Thunderbird shortcut on your desktop. On the Shortcut tab select change icon. You will get a Windows error telling you it can not find %ProgramFiles%\Mozilla Thunderbird\thunderbird.exe Click Ok. In the next dialog which shows your dots icon. Paste %ProgramFiles(x86)%\Mozilla Thunderbird\thunderbird.exe into the text box with the file name, replacing what is there. Click Ok. Select the correct Icon. Ok your way out of there and you should have the correct Icon.

Now to work out how this comes to be. Please goto Help menu> Troubleshooting information

And copy and paste (Ctrl +C or right click to copy) the Name, Version and UserAgent information into a message here. Then go to the Build configuration and click on it. Click on the link for Built from and paste that link here as well. I think I am going to be spending time talking to developers and that information will define the build your using exactly.

I see a bug coming round. Your other computer is fine, can you check if you can actually change the icon with out the error message (cancel will back you out or just update it if you get the error.

Is it the same version? It is my intention to file a bug on this, but the more information I can give the developers about what versions are affected the better I will get on.

Matt, Thank you for working with me on this. I will give you all the the info you need, but first let me explain how your icon fix did not work for me, and how I partly fixed them another way. Instead of a desktop TB icon which I don't have, I selected the icon on page 2 of start menu and selected properties and clicked change icon. There was no error message. I selected the blue bird icon and continued past administrator permission and the icon was fixed. That is one icon down, still two to go. The TB icon pinned to the task bar would not let me select properties, so I unpinned it, and it automatically moved to the first page of the start menu showing the correct icon. Then I dragged it back to the task bar where it correctly displays the blue bird. See the first screen shot. That is two icons down, one more to do. The third icon is the one attached to the TB exe file in the TB program folder. That icon has me stumped. See second screen shot. I can find no way to change it. So do you still want all the same system info you asked for?

Yes please to the info... I did file bug 1118057.

You might need to rebuild that icon cache again to fix the exe program, I think Windows dips into that cache instead of reading the icon from the file.

Trouble shooting information: Name Thunderbird Version 31.3.0 User Agent Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 Application Build ID 20141127140543 Built from https://hg.mozilla.org/releases/mozilla-esr31/rev/12cc454c851d

Is this all the info you need? Did you want this same information from my trouble-free computer?