As a follow on from the above, I tried an American programme called RegSweep to try to identify problem. Whilst downloading it,it stated that something on my machine was currently suspended and did I want to override this. Instead of noting the particulars of the "suspended" item, I clicked Yes and Regsweep swung into action. Having found "hundreds of errors" in my Registry, I then found RegSweep was not a freebie and for it to remedy matters involved a substantial purchase. Having clicked off and uninstalled it, I am back to square one as far as downloading the necessary upgrade to the Service Pack ie it wont install !
Help still required.