Well...
Many programmers can easily create things that are not detected by antivirus.
I myself made a remote admin tool, which could be used as a trojan quite easily. No antivirus on the market picked it up. Even though I used it to remote admin a business owners servers, (with that customers permission of course), and watch over their IT and accounting people. It could have been used for many things... That is the reason I keep it to myself and the client. Only we know it's there and what it does. Do you understand?
* So your entire theory about scanners rendering a machine 'clean' is pretty much not real. Because if a simple person like myself can write something in c++ that lets me remote admin a server under the auspices of antispyware without ever being detected, then it just goes to show you that anyone else can do the same.
All you are doing, with your knowledge, is removing what antivirus vendors have identified as a virus or trojan or some other malware. Which is fine and I don't care to argue semantics with you.
I would like to point out, that using the technique you guys use... You cannot ever guarantee the machine is 100% clean when you give it back to the customer.
It's not even a question in my mind. at all. ever. period.
This is exactly why most of the big chains lift the users documents, reformat the drive, then reinstall the os, drivers, and finally the documents.
Make of it what you will... It is what it is. Anyone can write a virus or trojan or remote admin tool. <wink>
I don't write viruses (code that replicates) or trojans (code that replicates and sabotages). It is illegal, and if you deploy such code into the wild, you can be fined and imprisoned if they catch you. Remote admin tools do not fall under the same category. That's not to say that as a computer virus researcher I can't create them on my virtual machine and erase them, but I guarantee you, that if someone as thick as me can do this, there are others who have done much more.
You may send back a pc that you scanned with 5 different scanners thinking it is clean as a whistle. That same machine you give back could be compromised by something you and your scanners dont even know exists. So you are giving back an infected machine.