What exactly are you using Firefox for? You don't need a "program associated with it" in order to browse the internet.

Don't think it is directly related to XP but certainly it is time to move away from that. A modern browser would likely work better on a modern Operating System.

There are some malware infections that make it hard to run programs (EXE) files. Hopefully you do not have one of those.

Could you check whether it is a problem with your shortcut by starting Firefox a different way:

Start menu > Run, type or paste the following and then press the Enter key or click Go:

firefox.exe

Thanks jscher, I've tried starting through 'run' without success, so I will have to get my PC checked for malware.

When I booted the PC today 'Avast' also failed to load up automatically. I have tried to load Avast from the desktop, but am being told it's the same problem: "no program associated with it".

I've still got Internet Explorer at the moment (which is how I am able to communicate with you), but for how long?!

Thanks Tony, I will probably have to update to a modern operating system as you say. Windows Security Essentials is no longer supporting Windows XP and my PC is too old for Windows 8, I might check out it's capability for Windows 7 first?

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

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

Did this fix your problems? Please report back to us!

Do a clean reinstall and delete the Firefox program before (re)installing a fresh copy of the current Firefox release.

Download a fresh Firefox copy and save the file to the desktop.

• Firefox 29: http://www.mozilla.org/en-US/firefox/all.html

If possible uninstall your current Firefox version to cleanup the Windows registry and settings in security software.

• Do NOT remove "personal data" when you uninstall your current Firefox version, because this will remove all profile folders and you lose personal data like bookmarks and passwords including data in profiles created by other Firefox versions.

Remove the Firefox program before installing that newly downloaded copy of the Firefox installer.

• (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
• (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

• It is important to delete the Firefox program to remove all the files and make sure that there are no problems with files that were leftover after uninstalling.
• http://kb.mozillazine.org/Uninstalling_Firefox

Your bookmarks and other personal data are stored in the Firefox profile folder and won't be affected by an uninstall and (re)install, but make sure that "remove personal data" is NOT selected when you uninstall Firefox.

• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Profile_backup

• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Clean_reinstall

I have tried all the malware scans you suggested Fred, but the first four would not download, presumably because they are also .exe files like firefox and Avast which won't launch. The fifth; ESET did download however (a .cab file I noticed) and scanned my PC for over eleven hours, but found no threats!!

As for Microsoft Security Essentials, they stopped supporting Windows XP in April. So I now have no protection from either MSE or Avast.

Okay, the situation we have is this. Windows, just like Firefox, has in it a database that tells the computer what to do with what type of file. The problem is that something has removed or changed the Windows listing on what to do with an exe file. You will need to get into the guts of Windows where this information is kept, and repair the damage.

Try this from Microsoft's forums: http://social.technet.microsoft.com/Forums/windows/en-US/7d2fb0fe-dd29-418a-87f5-89021ab5fa0e/this-file-does-not-have-a-program-associated-with-it-for-performing-this-action-please-install-a?forum=w7itprosecurity - there actually are several different suggestions.