A possibility, Ron, is that somewhere along the line, some Malware has been removed, leaving a registry entry looking for a file that no longer exists.
Plenty of ways of checking the registry. I just use the free edition of "Ccleaner". Its registry checker is very easy to run.
I have carried out all of your kind suggestions unfortunately to no avail, I am still stuck with the problem. Short of attaching high explosives to my pc & blowing the bloody lot up in the air can anyone please suggest an alternative ?