I was troubleshooting a Dirty Environment Found error while Microsoft Deployment Toolkit (MDT) 2013 was installing Microsoft Office Professional Plus 2010. The error was caused because Microsoft Office Professional Plus 2010 was rebooting the desktop after its installation and the reboot was disrupting the MDT task sequence.
I was using the Office Customization Tool for the installation of Microsoft Office Professional Plus 2010 but I was unable to find a dialog box that would allow me to suppress the reboot. After some quick research I found the solution. In the Office Customization Tool navigate to Setup > Modify Setup properties then add a property value with a Name: of SETUP_REBOOT and a Value: of Never.