Thanks for the pointers. I already use Ad-Aware as part of my protection arsenal but I will try Process Explorer. A memory leak was my first thought, but I haven't (knowingly!) installed any new software other than Windows updates and Symantec definition updates for some weeks whereas the problem is just a few days old. Yes, the memory footprint changes "by itself" and shutting down all Applications never brings it back below 1GB vs 750MB directly after startup. Something, somewhere, therefore appears to be orphaned or running quietly by itself.
None of this explains though why total apparent CPU usage is not the same as adding up the individual process consumption of CPU.
Cheers.
Last edited by The late XV105; 3rd Sep 2009 at 12:16.