>>I have existing sites running DotNetNuke 3.X and would like to upgrade them to the DotNetNuke 4.x code so that they are running under .NET version 2.
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>>Has anyone done this successfully? I've followed steps from the DotNetNuke website, but none work. I end up with either SQL Server errors or "module can't load" errors.
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>I have. It was a simple process for me. I don't use any fance 3rd part modules other than active forums...

I don't use any 3rd party modules only the included ones. Which steps did you use?