Hi again,
I am pleased to report the problem has been resolved
With your refrence to W7 installation problem I ran sfc /scannow in cmd prompt (run as admin) and it found several errors which it repaired.
I had to uninstall and reinstall PCMatic as it reported that the software was corrupt and now all is working.
One more thing, the steps in the link http://8help.osu.edu/3618.html can only be done if you have Windows 7 Professional or Ultimate not Windows 7 Starter, Home Basic, and Home Premium editions.
Thanks again for your help