I am going to attach the template include that we are using; it is included in our deployment templates and is set to run in the SYSTEM CONFIGURATION steps of the template. Essentially it uses CSCRIPT.EXE to call the SLMGR.VBS script and it includes a switch that supresses dialog boxes and forces WIN7 activation using the product key that was entered during sysprep.
Personally, I like having most things outside of my UNATTEND.XML file so that it is easy to turn them on/off as desired. I generally don't activate my clients until I know that i have my deployment template working correctly, and so I wait to include THIS template until the very end.
I hope this helps.
~IncludeWin7ProductActivation.xtp.zip 948 bytes