Let’s do a full clean re-install; Download Firefox For All languages And Systems {web link} Save the file. Then;

Using your file browser, open the Programs Folder on your computer.

Windows: C:\Program Files C:\Program Files (x86) Mac: Open the "Applications" folder. Linux: Check your user manual.

Do Not remove the profiles folder.

Look for, and rename any Mozilla or Firefox program folders by adding .old to them. Do not rename the Mozilla Thunderbird folder.

After rebooting the computer, run a registry scanner. Then run the installer. If all goes well, remove the OLD folders when you are done.

If there is a problem, start your Computer in safe mode and try again.

Starting The Computer In Safe Mode;
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I did all that but still experience the same problem.

I can install FF fresh - the only thing i want to do is to save the bookmarks and I guess know what registry keys to remove.

Do you mean you can see thumbnail images of your open tab(s) along the Windows 7 Taskbar, but clicking one does not open that window?

Sometimes Firefox's window gets "off screen" somehow. You often can force it to appear on the screen by right-clicking the little thumbnail image above the Taskbar and choosing Maximize. Does that work?

One possible cause for this is that the file which stores window sizes and positions has become corrupted. You can remove that file and Firefox will return to standard window sizing/positioning.

Method #1: If you can get a maximized window:

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" button > Troubleshooting Information
• (menu bar) Help > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, click the "Show Folder" button. This should launch a new window listing various files and folders in Windows Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > "power" button
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename xulstore.json to something like xulstore.old. If you see a file named localstore.rdf, rename that one to localstore.old.

Start Firefox back up again. Do windows display normally again?

Method #2: If you cannot get a Firefox window at all:

Shut down Firefox by right-clicking the taskbar icon > Close All Windows.

Using the Run dialog (windows key + R) or the Start menu search bar type or paste the following and press Enter to drill down to the Profiles folder:

%APPDATA%\Mozilla\Firefox\Profiles

Here you may see one folder -- in which case, double-click into that -- or more than one folder -- in which case, double-click into what looks like the most recently updated.

Scroll down and rename xulstore.json to something like xulstore.old. If you see a file named localstore.rdf, rename that one to localstore.old.

Start Firefox back up again. Do windows display normally again?

Then, to turn different bars back on, you can use one of these methods to show the toolbar list and select the desired bars there:

• right-click a blank spot on the tab bar (or the "+" button)
• tap the Alt key to activate the classic menu bar > View > Toolbars
• in Customize mode > Show/Hide Toolbars (see: Customize Firefox controls, buttons and toolbars)

To turn on the Menu Bar, Bookmarks Toolbar, or other bars, click it on the list.

>>Do you mean you can see thumbnail images of your open tab(s) along the Windows 7 Taskbar, but clicking one does not open that window?

Yes - exactly that.

>>Sometimes Firefox's window gets "off screen" somehow. You often can force it to appear on the screen by right-clicking the little thumbnail image above the Taskbar and choosing Maximize. Does that work?

Do you mean the thumbnail of the open FF tab or what?

>>Method #2: If you cannot get a Firefox window at all:

This method worked for me. I only found xulstore.json, which I renamed xulstore.json.old - do the new names matter?

What is the difference between xulstore.json and localstore.rdf ?

A huge thank you...... It now works for me!

Regarding the right-clicking, yes, you should be able to right-click any thumbnail corresponding to a resizable window and use the Maximize command on that menu. Whether it appears on the monitor is another matter... normally it does.

The new name of xulstore.json isn't critical, Firefox only looks for the exact name as far as I know. As long as you know what it is in case you need to restore it.

If you didn't find a localstore.rdf file, that's fine, it would only be present if you starting using Firefox quite a while ago.