I have since managed to resolve it - or at least, I hope I have.
I noticed that I had acquired an extra Add-On in Firefox called "NT Helper Class". It didn't look right as a) I didn't remember installing it, and I am pretty careful about what I install and b ) it just had an option to disable it. There was an uninstall button but it remained greyed out.
I disabled "NT Helper Class"
I smelt a rat so went to Google to see what I could find about this so-called "Add-on"
Discovered that it was associated with something called "Internet Saving Optimizer"
Checked the registry and found one instance of "Internet Saving Optimizer" there. Could not find it on the hard drive although searched hidden files and folders. Was unable to find "NT Helper Class" on hard drive or in registry.
Downloaded IObit Security 360 from http://www.iobit.com/security360.html
Ran scan and it found 274 problems, most of which were caused by Adware.DoubleD
It removed these and I had it create a log called "IObit Security 360 Report" which I saved as a .txt file
I then ran a more complete scan and it found 7 more instances of problems which it also removed
I created a log called "IObit Security Report a"
I am appending these logs to this message in case they could be of use to anyone else. I will run the other diagnostic software and append the logs from these too if you feel they would be of use
My machine is now booting more quickly, running more smoothly and it process load has dropped.
My concern is whether to leave IObit Security 360 running on my machine or not. It detects malware but I don't know if this includes virus definitions. Also I have Norton Internet Security 2009 and Spybot running on my machine. I am somewhat disappointed that neither of these were able to detect the problem. However, too many security programs on a machine can mean none of them work successfully, so I am not certain what to do.
Please let me know if you would like me to repeat the scans I ran when I first posted about the problem and many thanks for your wonderful website. It is a goldmine and I can see myself spending quite some time here.
Edited by jandun, 28 September 2009 - 08:53 PM.