I use AVG Free combined with Zone Alarm firewall, Spywareguard, Spywareblaster and MPVS Hosts file. I occasionally get tracking cookies but nothing else for the last 6 or 7 years.
I keep track of what's going on with HijackThis.
I use Ad-Aware, SpyBot S&D, Malwarebytes, for scanning. CleanUp and/or Wise Disc Cleaner for cleaning and I use Auslogics for defrag.