Systems Management

you can get it off a machine it is installed on by using something like

http://pcsupport.about.com/od/productkeysactivation/ht/findof2010key.htm

or you can deploy the install, do not remove the downloaded file, expand and get the code from the msp in the kace directory on the local machine.

i was just looking for the same thing, followed the directions located here

http://www.itninja.com/blog/view/how-to-track-windows-and-office-product-keys

they worked perfectly. 

In general, if the product keys are unencrypted, you can use a custom inventory rule to get them.

If they are (like Office), you would have to use a third party utility to obtain them:

http://www.itninja.com/question/how-to-track-windows-and-office-product-keys
http://www.itninja.com/question/kace-questions
http://www.itninja.com/question/pull-product-keys-for-ms-office-and-adobe-products?from=appdeploy.com

I've only seen one open source tool so far, but there might be others: http://sourceforge.net/projects/ekeyfinder/

your doing it wrong....