Catch,

Ok, will answer your question, and hopefully you will answer my last question?

Don't know what AIX is, but assume it is some sort of UNIX system?
From your reasoning it sounds like you are trying to say UNIX is secure, NT/2000 can be as secure too, if you configure it right.

I think that is almost a little too simple comparison. Windows is a much bigger target than UNIX is. Way more viruses for Windows. However, if Windows didn't exist, and UNIX was the biggest one out there, I would imagine all the virus writers concentrating all their effort on UNIX instead of Windows, and they would most surely come up with a whole bunch of successful viruses for UNIX as well.

So "why not"? I guess because there are hardly any viruses for UNIX. UNIX is just not a big target.