As you know, the next build of Windows Server (RS3) will be available only without UI and this means work via PowerShell or Command. Windows Server will introduce many new features about hyperconverged, storage, network, security and much other. If you are using the public preview, you could probably found this kind of error during map of remote share.
This error appears when attempting to map a network drive, and the network drive is configured to allow guest access, which means that the network drive can be mapped without the need to provide a username or password. One of the reason is that your computer is a member of an Active Directory domain, because one or more Active Directory Group Policy Objects (GPOs) may not allow guest access to network drives.
To resolve the problem is necessary map the remote drive with the parameters /user (net use z: \\10.10.200.1\public /user:admin).