Its a known issue that the w3wp process can spike processor usage every few minutes, are there any known solutions? googling only reveals a patch from microsoft that the server admin (i work applications on the client) won't install for unknown reasons. This server is running software that monitors anesthesia durring surgeries, so when 4 instances of w3wp all peg out at the same time and things stop responding on the client side, its a big deal.
What version .net are you running? I'd try recreating the application pool.