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.

You can also use ABP

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

Note that your System Details List shows that you have a user.js file in the profile folder to initialize some prefs on each start of Firefox.

The user.js file is only present if you or other software has created it, so normally it wouldn't be there. you can check its content with a plain text editor if you didn't create this file yourself.

The user.js file is read each time you start Firefox and initializes preferences to the value specified in this file, so preferences set via user.js can only be changed temporarily for the current session.

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

You may wish to see if a addon is causing your troubles too, by using Firefox safe mode as a troubleshooting step, see the article below.

• Diagnose Firefox issues using Troubleshoot Mode

My problem started two days ago when I was looking for a site to install ccleaner. I tried renaming iehelper.exe firefoxhelper.exe, chromehelper.exe, ending the programmes and deleting them. That did not help. I even tried the same with ituneshelper.exe. That did not help. I then looked in firefox\tools\addons\extensions and there it was. websteroids had been secretly installed and avast online security disabled. I deleted websteroids, enabled online security and goodbye friends checker. I have just rebooted and so far no sign of it....... Sorry - spoke too soon. Websteroids was back an hour later.

Do a malware check with some malware scanning programs on the Windows computer.
Please scan with all programs because each program detects different malware.
All these programs have free versions.

Make sure that you update each program to get the latest version of their databases before doing a scan.

• Malwarebytes' Anti-Malware:
  http://www.malwarebytes.org/mbam.php
• AdwCleaner:
  http://www.bleepingcomputer.com/download/adwcleaner/
  http://www.softpedia.com/get/Antivirus/Removal-Tools/AdwCleaner.shtml
• SuperAntispyware:
  http://www.superantispyware.com/
• Microsoft Safety Scanner:
  http://www.microsoft.com/security/scanner/en-us/default.aspx
• Windows Defender: Home Page:
  http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
• Spybot Search & Destroy:
  http://www.safer-networking.org/en/index.html
• Kasperky Free Security Scan:
  http://www.kaspersky.com/security-scan

You can also do a check for a rootkit infection with TDSSKiller.

• Anti-rootkit utility TDSSKiller:
  http://support.kaspersky.com/5350?el=88446

See also:

• "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked

I think I have got rid of friendschecker so fingers crossed. I found that it kept coming back until I discovered websteroids in the extensions and deleted it.... but it came back. I could not uninstall websteroids from the control panel so I crossed my fingers and deleted the websteroids folder in C:\Programmes. That got rid of friends checker as well. Then I discovered "better experience" in the extensions, deleted it and uninstalled it from the control panel. As I said, fingers crossed.

Yes my friendschecker is definitely gone. Watch out because there are a lot of sites out there giving false fixes to confuse you and make you give up! Firstly, I followed this advice which may have been a red herring. Try skipping it. I opened the Start Manager and in processes opened the file location of iehelper.exe, chromehelper.exe and firefoxhelper.exe, changed the exe extensions, ended the processes and deleted the files. That did not help!!! Secondly I deleted the Websteroids extension in Firefox\tools\addons\extensions and because you can't uninstall websteroids from the control panel, I took a chance and deleted the Websteroids folder from C:\programmes. Then "better experience" appeared in the firefox extensions so I deleted it and uninstalled that from the control panel. I have now had a couple of days clear of friendschecker. Incidentally, whatever installed Websteroids, better Experience and Friendschecker also disabled Avast Online Security from my Firefox extensions and Avast could not see it so make sure your virus scanner is up to date and running and scan regularly.