A couple of quick things to try. Have you re-started your computer? Have you tried on the desktop shortcuts - right click>open?

And a couple of questions. Is Firefox working properly via the URL Bar and the Search Bar? Do bookmarks open normally?

Alan I tried the top paragraph 2 times and no luck. Firefox opens fine and all bookmarks work fine if i click on a website link in a e-mail. Please explain the URL bar and search bar so I know for sure how to check that for sure. Thanks for your help.

The URL Bar is also known as the Location Bar and the Address Bar, and Firefox calls it the "Awesome Bar" when it is combined with the Search Bar.

None of this is complicated - you enter into the URL Bar the address of the website you wish to visit e.g. https://support.mozilla.org/en-US/. Firefox actually fills in the http or www for you. If you want to know what URL stands for, you enter "URL" into the Search Bar for Google or similar to search for that term.

If right click>open doesn't work on the desktop shortcuts, you need more expert help.

Alan when I attempted the download a trojan horse was caught by windows firewall. I think something still got through, because everything is very slow now or not working at all. Thanks for your help.

It is called Location Bar ever since though it is sometimes called Address Bar for those used to IE and the Awesome Bar was a nickname used for a period in the past.

If you are getting prompted to install stuff then you may have some malware on your computer perhaps.