Ansible does support Windows with an entire set of modules. Thus it is also possible to run Ansible playbooks targeting Windows systems right from Ansible Tower. However, since Windows does works via WinRM and not SSH, the appropriate variables must be set in the definition of the inventory of the machine:
The given screenshot shows the variables for Ansible 1.9. For 2.0 and above the variables are a bit different. Also, keep in mind that you might need to create an additional set of credentials.