All right. I've had it!

[orange]

I use Firefox and Kerio firewall, and don't have any problems now. Try 'Adware Away' its good. 'Process Explorer' is a very nice program that will show you a lot of information about active tasks. check every run key in registry to see what starts at bootup (search for 'runonce' and then look at 'run' key above it). most important is to not install anything suspicious, of course, just use programs that are best/safe especially those with 'green' install (just unpacking).

[orange]

yes, antivirus usually makes computer slower, but NOT IF YOU DISABLE 'real time' scan. Install KAV, then prevent it from starting at boot up , and disable two services it creates. everytime you wish to install something scan it manually (updating the signatures first).
IMHO, antispyware isn't essential once you clean your system, you won't need it again if everything is configured right. of course, use EMULE for all er.. needs.. ;-)