@ goranilic
From your list I would get rid of spybot s&d, Threatfire and keep the rest.
wth. I like SpyBot.
Gor, there
are multiple layers of protection you can have, but you need to be careful not to have multiple antivirus programs installed simultaneously. AV programs' primary function is as something called TSR (Terminate and Stay Resident,) which means the Antivirus runs in the background and acts accordingly when it needs to. If you have mutiple AV's installed at the same time, they can sllloooowww your system down by scanning each other or the same files you're trying to access, together, all day long. There are other programs called antispyware or antimalware, which don't scan your system in the same fashion, and thus don't conflict with your antivirus. Among these antispyware programs, some of them edit your Hosts file or registry to block installation of certain spywares, while others are used to scan your computer for spyware to discover if any are installed. SuperAntiSpyware, Malwarebytes' Anti-Malware, and Ad-Aware only run scans when you tell them to check for spyware (unless you pay, and it will schedule it.) SpywareBlaster edits the registry and host file to block spyware installations. SpyBot does both.
Okay, so first thing... Norton sucks. Never use Norton. Ever.
Second, Avast is wonderful as an Antivirus software. It's free and imo, it works at least as well as Trend's PC-cillin does, if not better.
Third, with regard to "multiple layers of protection," I would suggest installing SpywareBlaster, SpyBot, SuperAntiSpyware AND Anti-Malware.
Use SpyBot's immunize ability and SpywareBlaster to prevent certain programs from ever installing.
Use SuperAntiSpyware and/or Malwarebytes' Anti-Malware to scan for spyware if you're suspicious that any could be installed on your machine. These two programs have better active scanning abilities than SpyBot does, but I find that SpyBot's Immunize option works well.
And, of course, use Avast!. I got a virus/malware once with AVG, that Avast! would have detected.