Si por "disco virtual" te refieres a conectar a una unidad de red, puedes utilizar:
Public Declare Function WNetAddConnection Lib "mpr.dll" Alias "WNetAddConnectionA" (ByVal lpszNetPath As String, ByVal lpszPassword As String, ByVal lpszLocalName As String) As Long
Public Declare Function WNetAddConnection2 Lib "mpr.dll" Alias "WNetAddConnection2A" (lpNetResource As NETRESOURCE, ByVal lpPassword As String, ByVal lpUserName As String, ByVal dwFlags As Long) As Long
En http://www.mentalis.org/apilist/WNetAddConnection.shtml y http://www.mentalis.org/apilist/WNetAddConnection2.shtml está la documentación y un ejemplo de cada una.