You can disable blank password restrictions by using a policy. To locate and change this policy:
1. Click Start, point to Run, type gpedit.msc, and then click OK to start the Group Policy Editor.
2. Open Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options\Accounts: Limit local account use of blank passwords to console logon only.
3. Double-click Limit local account use of blank passwords to consol logon only.
4. Click Disabled, and then click OK.
5. Quit Group Policy Editor.
Now to login via remote desktop with a user that has no password, usually for an media box, but beware that this does not provide any security what so ever if you were to expose that PC to the outside world.
Microsoft Support Article KB303846