Where do you want the clock to appear?

Is the problem that the Windows task bar clock is getting hidden when you use Firefox in full screen mode?

I want the clock in lower right. The clock is hidden for all selections except the first appearance of Mozilla screen, not just in full screen.

Is the Windows Task bar set to be always on visible and on top (right-click context menu)?

where or what is Windows Task bar and what is (right-click context menu)

where or what is Windows Task bar and what is (right-click context menu)

The Windows task bar is the bar that usually appears at the bottom of the screen with the Start button at the left and (usually) the system clock on the far right.

If your Task Bar only appears when you mouse over it, this Microsoft support article describes where you can change that "auto-hide" setting: Microsoft Windows XP - Hide the taskbar.

While Firefox normally doesn't intrude into the space of the task bar if it's there, sometimes the file that stores Firefox's window size settings can become corrupted. If necessary, you can delete the file, then Firefox will return to your default toolbar arrangement and window position/size.

Open your current Firefox settings folder -- also known as your Firefox profile folder -- using:

Help > Troubleshooting Information

On that screen, click the "Show Folder" button to launch a new Windows Explorer window listing your settings files.

Without closing that new window, switch back to Firefox and Exit (e.g., Firefox button > Exit or File menu > Exit).

Pause while Firefox finishes its cleanup.

Then, scroll down through your settings files and find localstore.rdf. Rename that file to something like localstore.old (this way, it's still there in case you want to use it again).

You're done in that window and you can close it.

Restart Firefox.

Thank you very much