ASP.NET

Dim sFullPath As String = sServer + sFolder + sFile

Dim wcClient As WebClient = New WebClient()

Dim obj As UserManager = New UserManager
obj.CreateIdentity("user1", "Server1", "password")

Dim buffer As Byte() = wcClient.DownloadData(sFullPath)

Response.ClearContent()
Response.AddHeader("Content-Disposition", "inline; filename=userdoc" + oDocument.FileExtension.ToString)
Response.ContentType = returnExtension(oDocument.ContentType.ToString)
Response.AddHeader("content-length", buffer.Length.ToString)
Response.BinaryWrite(buffer)

obj = Nothing

Declare Auto Function LogonUser Lib "advapi32.dll" (ByVal lpszUsername As String, _
    ByVal lpszDomain As String, ByVal lpszPassword As String, ByVal dwLogonType As Integer, _
    ByVal dwLogonProvider As Integer, ByRef phToken As IntPtr) As Integer

   Declare Auto Function CloseHandle Lib "kernel32.dll" (ByVal handle As IntPtr) As Boolean

   Public Sub CreateIdentity(ByVal User As String, ByVal Domain As String, ByVal Password As String)
       Dim tokenHandle As New IntPtr(0)
       Dim ret As Integer
       Dim LOGON32_PROVIDER_DEFAULT As Integer = 0
       Dim LOGON32_LOGON_NETWORK_CLEARTEXT As Integer = 3

       tokenHandle = IntPtr.Zero
       Dim returnValue As Boolean = LogonUser(User, Domain, Password, LOGON32_LOGON_NETWORK_CLEARTEXT, LOGON32_PROVIDER_DEFAULT, tokenHandle)
       If False = returnValue Then
           ret = Marshal.GetLastWin32Error()
           Throw New Exception("LogonUser failed with error code: " + ret.ToString)
       End If
       Dim id As New WindowsIdentity(tokenHandle)
       CloseHandle(tokenHandle)
       id.Impersonate()
   End Sub