've used both Norton and McAfee Security Suites and both allowed spyware cookies and other crap on my computer and those at my office and they are both system resource hogs. I just uninstalled the McAffee Suite that came with my laptop and went back to my normal setup - freed up over 100Meg of RAM and now I don't have 8-10 pieces of spyware/adware on my computer after every web session. I have a combination of programs (most of which are passive blocks that don't use any system resources after they are loaded and updated) that are all free to home users to block this crap with 99.9% effectiveness. I use:
Spybot Search and Destroy (the immunization works passively)
Adaware (for a secondary cleaning program with Spybot)
CleanUp! (after each web session - doesn't clean as deeply as some you have to pay for but along with MRU Blaster and a once a week use of SpyBot or Adaware to clean usage tracks it stays cleaned up)
Zonealarm (free version- I had ZA Pro at one time and really liked it but I wouldn't buy it with any of their other security stuff)
Over the years I have tested this "suite" of programs against purchased cleanup and protection programs and have found that these get it as clean, and keep it as clean and safe as the suites you have to pay for.
Oh, and I tried to use AVG, but it didn't like my ISP's pop server and would block ALL incoming email unless I disabled the email scanner and even workinng with their tech support didn't solve it. Their solution was to upgrade to a purchased version, but they couldn't guaranteee that would work either so what was the point. Besides the email issue, I really liked it.
XD .45 Service Compact