Bartender Print Engine Start Fail

I'm a very new to use the sdk.

I tried to run the sample project "LabelPrint" in the debug mode .

it always failed when i try to start a bartender print engine

i'll explain to u via the sdk's sample code.

following is the sample code in the sdk that i capture:

Public Sub Demo()
' Initialize a new BarTender print engine.
Using btEngine As New Engine()
' Start the BarTender print engine.
btEngine.Start()

' Open a format.
Dim btFormat As LabelFormatDocument = btEngine.Documents.Open("C:\Format1.btw")

' Print the format.
btFormat.Print()

' Stop the BarTender print engine.
btEngine.Stop()
End Using
End Sub

this program cannot run to "open a format"

following is my environment:
vb .net 4.0 / WindowsFormAppication type / vs 2010 / win7