Detection of unauthorized software

I'm assuming you're referring to spy programs.
You can go to download.com and then Utilities/Security & Encryption. From there you
can download Ad-aware 6.0 - its free.
Install this program and then run it on any pc
you want.
Its pretty good in removing spy softwares.

If you are talking about a software audit program then try AIDA32, you can download it from the site below;
http://www.freedownloadscenter.com/Reviews/r847.html

You install this on both the machine you want to audit from and the machine that you want to audit. Make sure that you explore all of the configuration settings. You have to enable the program to accept connections and then enable what it will allow you to do remotely. You can identify software and remove it remotely.

There are software packages that can scan systems over your network and provide a list of what software is installed.

I don't know if any of them specifically identify "unauthorized" software.
You may be able to configure some of them to compare a PC to a previously stored configuration and report changes.

Here is my list of links.

http://www.aida32.hu/aida32.php

http://www.alliedhr.com/index.html

http://www.blueocean.com/default.asp

http://www.ezaudit.net/

http://www.networkview.com/

http://www.iinventory.com/page.asp?w=33&Ref=6

http://www.emco.is/

http://sourceforge.net/projects/winfingerprint/

Depending on the version of Windows, you might be able to set a group policy to disable installing software.

Chas

belarc advisor

www.belarc.com

Baleric isn't free if you're deploying in a Corporate enviroment, but it is very good :)