I wonder how you are so certain that you have never been infected. People believing that their systems will not get infected if they are "careful" are prime examples of the Dunning-Kruger effect in action.
Well my other machines have one of either Onecare, McAfee, Panda or Norton installed, set up fully up to date before being allowed on the internet. I've only ever found tracking cookies which don't bother me that much. Similar spec machines but only the Norton system has been slowed too badly. Maybe it's just I ensure their all patched.
My work job requires me to fully test MS and other patches before inflicting them on my 10,000 machines, so maybe I'm unusual in having all the boxes as protected as possible. I deal with infected machines from time to time, funny how it's always the people who "need admin rights to do my job". The biggest downside is they're usually directors who make the policy for everyone else but shout the loudest that we're not protecting them. And we claim the Americans don't get irony.
This win7 system - a service "avgsrv??" was causing the processor to hit 100% for hours, maybe I've got some wierd data on a back up drive it doesn't like.
Thanks CKurt will try that, after all this is only test not production system at home and I'd really don't fancy paying for a trial version of AV for it at this stage.