UPDATE: Tried various suggestions; then as suggested by MM (see above) I left AVG Free in place, went into Safe Mode and ran Rkill, Hitmanpro, then tried to run Combofix - this caused the system to crash.
I then uninstalled AVG Free and tried the above again, the system crashed again.
I then installed Avast (free) and tried again, the system crashed again.
None of the (free) Malware/Antiviral programs I tried found any problems or, indeed, any Crypt2 files.
As I couldn't get "Combofix" to run I finally (more in hope than expectation) emailed the Avast Help system. I received an automated reply immediately and a real reply within 24 hours, I have since had a further three immediate emails from Avast. Their last suggestion was: -
Run Avast in Safe Mode
Run Avast browser cleanup
Run Malwarebytes' Anti-Malware
Run Spybot
Re-boot
This procedure identified two Trojan Crypt2 files!
I am most impressed by the Avast Help system, so much so I will be buying their system. I anyone needs the full Avast procedure please PM me. Also many thanks for all the help given on pprune.