Windows 7: Spoolsv corrupts on boot

I have a problem with ‘spoolsv’ in that it appears to corrupt after every boot. I have to go to do the ‘sfc/scannow’ then restart the spooler to be able to print. I have tried many fixes but to no avail. I don’t think it is a printer problem since the same happens when I connect to an entirely different printer and even when I uninstall all printers!
I have now reinstalled Windows and initially the problem disappeared but has now reappeared initially when installing AVG – problem disappeared when AVG was uninstalled – now it makes no difference if AVG is installed or not, I have the problem after every boot.
One strange I have just noticed is that on boot the service ‘spoolsv’ is 43KB in size with the Digital Signature being Phoenix Technologies Ltd, but once I run ‘sfc’ ‘spoolsv’ is 545MB in size with the Digital Signature being Microsoft. I have run AVG, Malwarebytes and Spybot S & D in normal and safe mode but have not found a problem.
I am now at my wits end – has anybody seen this before or have ant ideas?
Apologies if I have put this post in the wrong place etc but this is my first post
The sytem involved is a Dell laptop (Studio 1555) running Windows 7 Home Premium 64 bit
The printer is HP photosmart S4280 – I have also installed a Canon IP4500 – but I don’t think either is a problem.
Thanks Barry