In this case we have both OS (Host OS = Windows7, Guest OS = Windows Server 2012 R2 Standard editon) on Windows OS.
In Host Os we created folder “SapInstall” where we put all SAP installation files and change setting for VirtualBox.

No we can go into VM Guest (Windows Server 2012 R2) run Explorer and we can see this

I recommend to copy whole folder into c:\ on Guest OS and remove setting Shared folder from VirtualBox.
The reason is, if you have active Shared Folders setting in VirtualBox during installation you can give this error.