Installing the Prerequisites for Bentley Desktop Applications on Windows 8, there is an error for but install can continue.
When starting MicroStation, there is a Windows message asking an internet connection to finish the install.
Even though it is already present on the machine, Windows 8 require an internet connection to activate the .NET Framework 3.5.
Follow the steps found on Microsoft website, on the page bellow, in the Trouble shooting section.
http://msdn.microsoft.com/en-us/library/hh506443.aspx