We have multiple wordpress installations on our IIS7 (Windows Server 2008) Server as follows:

http://www.example.com/site_one
http://www.example.com/site_two
http://www.example.com/site_three

These all work properly. However we would like to configure it so that when users visit the root domain (http://www.example.com/) or any page underneath, ie:

http://www.example.com/
http://www.example.com/page1
http://www.example.com/page2

They would actually see the corresponding pages for site_two:

http://www.example.com/site_two/
http://www.example.com/site_two/page1
http://www.example.com/site_two/page2

How could we achieve this?