I want to upgrade a DNN 4.3.5 to 4.3.7. I've tried to upgrade my production system after a complete backup and failed - the system contains some self developed modules and additionally  purchased third party modules. The first idea was, that my modules were wrong. So I installed a completely new 4.3.5, just changed a little bit the home page and the installed a new 4.3.7 and told in the web.config I want use the database from 4.3.5. After the compilation F5 (I'm using Visual Studio 2005), the browser will opened and correctly finishes the upgrade. When I try to open the portal the system tells me "The website can not be opened" (-> german: Die Webseite kann nicht angezeigt werden). The old system was http://localhost/DNN435 the new http://localhost/DNN437      

Please can you help me with the problem or do know a bullet-proof recipe for upgrade of dnn systems.

Thank you Antonio for your help but I'm still struck in this problem.

Actually I did the same way to upgrade the system but there must be a small but very importent difference you do. I think it must be the handling of the web.config file before I upgrade (compile and start F5 in VS2005) the system.

For the moment, just to find out my problem, I'm using a standard DNN 4.3.5. source and DNN 4.3.7 source(the ws is XP SP2 and MSSQL 2005). I compile the 4.3.5 and it starts without any problems. After the compilation the machineKey tag (the attributes validationKey and the decrytionKey) were changed but everything works perfect. Now I create the 4.3.7 system. I'm following two strategies to do the upgrade:

First: I create a new 4.3.7 folder and assign the ASP.NET machine account - unpack the source code to the folder - create a new virtual folder in the IIS (-> localhost/DNN437) - change the VS2005 project file (.sln) corresponding to the poaths - then do I update the web.config file (take the two keys and the data source) - I compile and start - the upgrade process starts and finishes without any errors - then I want to go to my portal ("Click Here To Access Your Portal") but nothing happens as there were be no site

Second: I copied the source code over the old one -  updated the web.config file - compiled and started - upgrades finished without errors - then I want to go to my portal ("Click Here To Access Your Portal") but nothing happens

The funny thing is - it's the same result without any errors. The database ist upgraded (it tells me in a later attemption that the current database version is 04.03.07) and the assembly is the current version (to 04.03.07). When neccesary (the first upgrade strategy), I added a second PortAlias (localhost/DNN435, localhost/DNN437) for the default portal.

 I'm really run out of more ideas to solve the problem. Any help is welcome.

Normally I try to let the framework code untouched. When upgrading, it brings along a lot of work and normally new errors. I develop multilanguge sytems (EN, DE) with customized desktop modules. There are a very, very few lines I have to change the framework but it is a must. In the future we'll try to sell this modules (asset management system). We' ve now  finished the "alpha site" version - in the past an upgrade was not really important, but now we will present the site and the modules.

Your 4 points are clear for me (the 3. when you have a XP using the local IIS but you've behind the firewall a AD with Win2003 Server and outside the production W2k3 server)

I think the next passage your writed is now very interesting: do you overwrite the keys (decryptionKey and validationKey) in your old web.config file (+datebase) with the new the come along with the new version (from release.config) and use it then or do you take the new web.config and insert your old keys ?