Debo construir un simple programa de instalación que copie un gran
archivo de 600 megas, desde un CD a un disco duro. La pregunta es, ¿cómo
puedo determinar el espacio disponible en un disco duro antes de copiar el
archivo.?

Private Declare Function GetDiskFreeSpaceEx Lib "kernel32" Alias "GetDiskFreeSpaceExA" (ByVal lpRootPathName As String,lpFreeBytesAvailableToCaller As Currency, lpTotalNumberOfBytes As Currency,lpTotalNumberOfFreeBytes As Currency) As Long

Private Sub Form_Load()
    Dim r As Long, BytesFreeToCalller As Currency, TotalBytes As Currency
    Dim TotalFreeBytes As Currency, TotalBytesUsed As Currency
    Const RootPathName = "C:\"
    Call GetDiskFreeSpaceEx(RootPathName, BytesFreeToCalller, TotalBytes,TotalFreeBytes)
    Me.AutoRedraw = True
    Me.Cls
    Me.Print
    Me.Print " Total Number Of Bytes:", Format$(TotalBytes * 10000,"###,###,###,##0") & " bytes"
    Me.Print " Total Free Bytes:", Format$(TotalFreeBytes * 10000,"###,###,###,##0") & " bytes"
    Me.Print " Free Bytes Available:", Format$(BytesFreeToCalller * 10000,"###,###,###,##0") & " bytes"
    Me.Print " Total Space Used :", Format$((TotalBytes - TotalFreeBytes) *10000, "###,###,###,##0") & " bytes"
End Sub