For years, I have quarrelled with Norton Anti-Virus on my PC. I suppose it does its job okay in terms of protecting me from evil viruses but it's an intrusive program that often seems to be hogging memory and slowing down others. It also has a teeth-gnashing tendency to go kablooey every now and then for no visible reason…and don't even try to get Tech Support online or, if you're a mad and impetuous dreamer, via phone. General rule of thumb: If you have Norton and something goes wrong, uninstall the program and reinstall it from scratch. It's a pain but that seems to be the only thing that works…and if that doesn't, try this: Uninstall it not the normal way but with a piece of software called the Norton Removal Tool (or something of the sort…you can Google and find it) and then reinstall. Or better still, uninstall it and keep it uninstalled forever and switch virus programs.
Which is what I finally did after way too many crashes and problems. I am now up and running — on the advice of Bill Goldstein, my tech support wizard — with AVG and it's doing the job well. Matter of fact, their AVG Malware package is both virus checker and spyware scanner, rolled into one. The spyware component was formerly known as Ewido, and it was one of the best. No spyware checker will catch everything so if you're anal about this kind of thing, you need to run a couple. (I rotate Spybot Search and Destroy, Ad-Aware, Super Anti-Spyware and A Squared. Each flags things the others don't, owing to different criteria of what constitutes "spyware.") But the AVG version is almost all you need.
There is a free AVG and a pay AVG. I sprung for the pay AVG and so far (one week), I'm very happy with it. For whatever that's worth.