how to know if your pc is acting as a zombie

How can the average bear pc user know if his pc is acting as a zombie pc?

Is there any simple or easy way of doing this?

As far as I can tell, it takes a pretty sporty degree of sophistication and software to be able to do that.

Yes, any two way firewall tells you of outgoing activity. However, a lot of outgoing activity is normal and useful.

So, how do you detect and identify unwanted outgoing activity?

 

You can use netstat
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/netstat.mspx?mfr=true

Or you can use Port Explorer to do the same; it is much easier. You will have to check each one that connects to the outside to see if legit. Google can help you with this. It is not as difficult as you may think; it is tedious though. Do it once then you only have to do the new processes when you install a new program with internet access.