What's nice about fancy and expensive products is that the vendor wants to win the customer's confidence by allowing evaluation periods. Microsoft will let you download Windows Server 2008 R2 to evaluate (test, that is), and the license is good for six months:

When you work with Windows Server, focus your learning on server roles, which is how a given server becomes a web server, a domain controller, a database server, and so on.

You can find the evaluation download at: https://www.microsoft.com/en-us/download/details.aspx?id=11093.