Harb,
I can't begin to remove cydoor without unpacking kazaa. I tried unsuccessfully all of last nite, then once you identified PECompact I had another go using specific tools but still no joy. Where did you get the info from ReaLiStry?
Programs are able to check for debuggers such as SI by checking for INT3 (interrupt 3) which is a breakpoint. i.e. stops program execution so you can examine registers, memory etc. Kazaa is one of those which will not run if it detects it. I will read up more on this to see if there is a way around it.