It could be that the localstore.rdf file in the profile got damaged. Try moving it out of the profile and then launch Firefox again. If that fixes the problem, you will then have to redo any customizations done to toolbars or window sizes. If that does not help, try getting the whole installer and install Firefox over again.

It is possible that the screen is too wide or too high and that the scroll bars fall off.

• Use Restore or Maximize in the right-click context menu of the Taskbar icon to set focus to the Firefox application if you do not see the Firefox window.
• Open the system menu of that Firefox window via Alt+Space and see if you can move and resize that window.

If that works then close Firefox (File > Exit/Quit) to save that setting.

See also:

• http://kb.mozillazine.org/Resizing_oversize_window

If the above didn't help then see:

• http://kb.mozillazine.org/Corrupt_localstore.rdf

Thanks for the help. The reinstall worked