We currently have a 64bit Windows Server 2003 running an instance of IIS 6 which was configured to run in 32bit mode. If we install the .NET framework 4.0, should the framework be installed as 32bit or as 64bit?

Note, this is a production web server which currently has .NET 2.0 installed and runs a classic ASP application as it's main website.

2 Answers 2


The architecture of the .net framework must be the same as the operating system you have installed. In your instance you will require the 64 bit version.

What actually happens on 64 bit is that you get both a 64 bit version and a 32 bit version, so your IIS application will load the 32 bit version.

You will need to configure your App Pools to run using .net 4 once it has been installed.


When you install the 64-bit version of the .NET Framework on a 64-bit system, both the 32-bit and the 64-bit ones get installed.

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