Determining Whether Server Core Is Running
Use the GetProductInfo function to retrieve the product information for the current operating system. If Server Core is running, one of three values will be returned by GetProductInfo: PRODUCT_DATACENTER_SERVER_CORE, PRODUCT_ENTERPRISE_SERVER_CORE, or PRODUCT_STANDARD_SERVER_CORE. Calling GetProductInfo is the recommended way to test if Server Core is running.
Another way to test if Server Core is running is to check the registry under HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion for the value of InstallationType. If it is set to "Server Core", then the Server Core installation option is installed.