i like how spybot will immunize your system from bad cookies, etc. i use avg anti-virus, spybot, and adaware together, and have never had a problem. then again, the best virus coders make it so you never know. mu ha ha
I probably should add that I use Norton 360, which is a very comprehensive anti-virus, firewall, anti-spyware, etc program. Some people don't like Norton for various reasons, but I have a business pack that I use on all my computers and it seems to do its job very well. To each his own, as is the case.
I use Windows Defender and PC Tools ThreatFire (both free) as recommended by Maximum PC and they've done the job. If you don't do anything shady, then it's pretty easy to keep your machine clean of spyware.
windows defender is a joke...like i trust microsoft to know its own program well enough to defend it. think about it...if they did know it well enough then maybe they would just patch the holes instead of forcing some piece of bloatware upon me that is windows defender.
I personally believe there is only one program worth paying for, Webroot Spy Sweeper. The active shield is great, the customized sweep options are good and at 19.99/yr its a bargain IMO.
For free virus protection I use AVG which has a resident shield built in that works great too. I also scan with adaware and use regscrub xp when im done with all my scans to clean up the registry.
Norton and McAfee are bloatware that will hijack your computer if you don't pay the exhorbinant fee every year to renew the subscription...its as bad, IMO, as most trojans as far as removing from your system. I use symantec endpoint protection here at work because it is forced upon me and it slows the system down to a crawl (p4 2.8 w/2GB of ddr400) when it decides it wants to randomly scan things.
I having been using McAfee for free for the past three years, since my school provides it free via download. I have given it to several friends, and everyone has said it was a major improvement over their previous protection. My favorite aspect is that you can set it to tell you when a program tries to access the internet for the first time. You wouldn't believe the things that try to hop online! My family used to use Norton, but it seems to be a virus in itself, but as was said before, to each his own.