This is a known issue with OneAgent Windows installer version <=139.185. The problem occurs only on Windows Server 2008 when the installer is launched in interactive mode.
To work around the problem you can launch the installer in quiet mode from Administrator's command-line as:
Dynatrace-OneAgent-Windows-1.139.150.exe /quiet /qn
If you need further assistance please open a support ticket on https://www.dynatrace.com/support/
Thanks...Will try and let you know.