Today just a quick tip, which may save you some time. If you want to connect to virtual machine with Windows 10 Technical Preview, make sure that you include DNS name in user name field. So instead of default combination of username and password

which worked for me for every virtual machine (except for the one with Windows 10). You should use something like that

If You don’t know the DNS name for virtual machine, you can easily check it in Virtual Machines pane