Not an expert with PPT; but there is no way to check whether a presentation
has got a password or presentations.Open do not have an option to pass the
password. Try the below which worked for me....which uses Sendkeys..
Sub Macro()
Dim pptApp As Object, strFile As String, strPassWord As String
strFile = "d:\Presentation8.ppt"
strPassWord = "password"
Set pptApp = CreateObject("PowerPoint.Application")
pptApp.Visible = True
pptApp.Activate
SendKeys "%F", True
SendKeys "O", True
SendKeys strFile, True
SendKeys "%O", True
SendKeys strPassWord, True
SendKeys "~", True
'Set myPPT = pptApp.Presentations(1)
'MsgBox myPPT.Name
End Sub