Is a Windows registry error responsible for Firefox opening two browser windows whenever I use a hyperlink from a Word file?

Question

Whenever I use a hyperlink from an MS Word document, Firefox opens two windows instead of one. The first window is the one I need. The second contains a message that the page could not be found and the address bar contains the URL appended with "Firefoxhtml/shell/open/command".
This problem is similar but NOT identical to one in MozillaZine headed "Windows error opening internet shortcut or local HTML file - Firefox". But none of the solutions in that article work for my problem: I've disabled all extensions but that hasn't helped. I've tried editing file types so that the DDE is removed (I'm not a teccie so have no idea what that means), but after following the instructions to the letter it doesn't seem to remove the DDE. Also I read that removing the DDE is not a good idea for people like me who need to open numerous firefox browser windows at one time. Furthermore, the MozzilaZine article refers only to problems opening a URL link in a MS Outlook email when Firefox is NOT running. My problem concerns the opening of URL links in MS Word when Firefox IS running!
I've run countless different virus programmes, rootkit checkers etc but they all come up blank. However, I did come across guidance on this website: http://antivirus.about.com/od/windowsbasics/a/shellopen.htm which suggests that something may have altered the shell open command for two registry keys used by Firefox.
# HKEY_CLASSES_ROOT\htafile\shell\open\command
# HKEY_CLASSES_ROOT\htfile\shell\open\command
The default value for each of these should be "%1" %*. But on my user, the default value reads:
(for htafile) c:\windows\system32\mshta.exe "%1"%*
(for htfile) c:\programfiles\windowsNT\hypertrm.exe"%1
What should the value be for these two files?
Can anyone sort this for me please? Bear in mind I'm not a teccie!

Answer 1

Do a malware check with a few malware scan programs.<br />
You need to use all programs because each detects different malware.<br />
Make sure that you update each program to get the latest version of the database.
*http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
*http://www.superantispyware.com/ - SuperAntispyware
*http://www.safer-networking.org/en/index.html - Spybot Search & Destroy
*http://www.lavasoft.com/products/ad_aware_free.php - Ad-Aware Free
*http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page
See also "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked and [[Searches are redirected to another site]]