DotNetNuke does not have any functionality for this, but a quick google search should get you an example of how to temporarily impersonate a user.

Just be sure to destroy the handle to the user properly so you don't leak resources.

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-Mitchel Sellers
Microsoft MVP, ASPInsider, DNN MVP
CEO/Director of Development - IowaComputerGurus Inc.


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I figured out this problem.  Please ignore this. I just want to include the solution if you are ok with it.  I was trying to check a directory using Directory.Exists .NET API. The call would return false.  I was trying to impersonate the windows logged on user in code but this is not possible when the mode is set to Forms.  
I added this line to my Default.aspx file
<asp:label id="myUserId" ><%= Environment.UserName %> </asp:label>
This gave me USR_account and this told me that the ASPNET account security is not using the integrated windows. When i set the account security on IIS to use only windows integrated security then my problem went away.
Sorry to have distracted you from your other posts but i think this will come in handy for others who may fall in the same whirlpool.
bramoin