10

Solved
Turned out to be a remnant of AVG antivirus still running in the background.
I had some problems about a month ago and used a couple of free antivirus programs to help flush out the culprit.
Having successfully done that without realising it my shields had been compromised on my avast installation. When i uninstalled Avast fully intending to reinstall an AVG remnant in my startup prevented me from re-installing my avast.
As is always the case once you know what the problem is its simple to cure.
deleted the startup entry and file lurking in my windows directory and rebooted and avast installed perfectly, i rebooted again to see if the original problem had gone and everything is fine my shields are on as they should be.
Thanks for your help and hopefully this thread will help someone else in the future.