I want to run a container with microsoft/windowsservercore.
This can be done if docker server's OS is windows. I couldn't find an answer for whether it is possible using docker-toolbox in windows 7.
No, Docker Toolbox installs a VirtualBox VM in which a minimal Linux is installed to run Docker Linux containers.
Running Native Windows containers requires Windows 10 professional, or Windows Server 2016.
Docker for Windows allows you to toggle between "Linux" and "Windows" containers, but also requires Windows 10 Professional or Enterprise