Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Mal-ware causes damage. Sometimes to the point that the computer can't even start. After you clear out a virus, check programs for problems. You may end up having to re-install some of them.

Perform a System File Check to fix corrupted system files http://www.sevenforums.com/tutorials/1538-sfc-scannow-command-system-file-checker.html

Download Firefox Full Installer 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.

Look for, and rename any Mozilla and Firefox folders by adding .old to them.

Now run the full installer. If all goes well, remove the OLD folders when you are done.

JBABath said

I have had a lot of problems with Vi-View infecting Firefox recently but I have successfully removed it. In the process of removed and re-installed Firefox. On re-installation, Firefox works perfectly. However, if I close the program and attempt to reopen it I have a problem. An icon appears in the task bar and if I hover over it, it shows a normal Firefox start tab. However, I cannot maximise the screen to use the program. If I try to bring it up, a reduced size image flies off to the right of the screen. I have IE11 and Chrome installed and I have checked them to ensure Vi-view is no longer present on the machine to ensure this virus was not the problem. My operating system is Windows 7 Professional, 64 bit. Any assistance gratefully received. I don't want to stop using Firefox.

Many thanks for the quick reply. I have done as you suggested. I ran SFC, which did not report any errors. I copied to a USB stick and then deleted all traces of Firefox from my machine, not only in the "Programs" directory but also in "AppData". I downloaded the UK specific Firefox Full Installer and reloaded the application. Everything is now working exactly as it should and Firefox is back as my default browser. Thanks again for your help.

Great to hear, Safe Surfing.