Jian,

Thank you for your reply.  Unfortunately, the code you
provided below will not work with my app because I am
using Forms Authentication and User.Identity is returning
a System.Web.Security.FormsIdentity object.  So I tried
using the following code:

  Dim impersonationContext As
System.Security.Principal.WindowsImpersonationContext
  Dim currentWindowsIdentity As
System.Security.Principal.WindowsIdentity

  currentWindowsIdentity = WindowsIdentity.GetCurrent()
  impersonationContext =
currentWindowsIdentity.Impersonate()

This seems to work without errors and
WindowsIdentity.GetCurrent() returns the account I am
specifiying in Web.config, but I still recieve Permission
Denied, the same error as before.

I did some more reading on the Impersonate() method and
there is an example using LogonUser, similar example from
the article you sent me.  I tried it but received the same
results.  Then looking in the documentation, the sample
there states:

' This sample demonstrates the use of the WindowsIdentity
class to impersonate a user.
' IMPORTANT NOTES:
' This sample can be run only on Windows XP.  The default
Windows 2000 security policy
' prevents this sample from executing properly, and
changing the policy to allow
' proper execution presents a security risk.

I am using Windows 2000 Server and so are all of my
customers.  Have you tried these examples with Windows
2000 Server?

Lastly, the LogonUser API documentation states it cannot
authenticate users against a remote computer, just the
local computer.  I am running Active Directory and all my
customers are as well.

Any other ideas to work around this issue?

Thank you very much for your time,
George