Aspnet_regiis in Framework64 folder for a 32 bit web app

Question

In a 64 bit system, is there any reason ever to use the aspnet_regiis in the Framework folder as opposed to that on Framework64? Even for an app compiled to x86 I know that just registering aspnet with the exe in Framework64 and setting the application pool to Enable 32 bit works.

So what are differences between the two?

Answer 1

I found the following on MSDN (http://msdn.microsoft.com/en-us/library/k6h9cz8h(v=vs.100).aspx):

The 32-bit version of Aspnet_regiis.exe adds only 32-bit scriptmaps to the Applicationhost.config file. The 64-bit version of Aspnet_regiis.exe adds 32-bit and 64-bit scriptmaps to the Applicationhost.config file. This is done because 64-bit versions of Windows Vista, Windows Server 2008, or Windows 7 installations that have IIS 7.0 enabled will also have Windows on Windows 64-bit (WOW64) support available.

Also,

There are 32-bit and 64-bit versions of Aspnet_regiis.exe. For Windows Vista and Windows Server 2008, you can run the 32-bit version of the tool on a 64-bit installation of IIS. This lets you run mixed 32-bit and 64-bit worker processes on the same 64-bit system. The following table lists special cases and limitations that apply when you run the 32-bit version of the tool on a 64-bit version of IIS.

Thereafter it explains specifics for IIS6.0/7.0 - quoting the part applicable to IIS7.0:

On Windows Vista, Windows Server 2008, or Windows 7, when you run the 32-bit version of Aspnet_regiis.exe under IIS 7, the tool does not automatically set the enable32BitAppOnWin64 attribute of the applicationPools element. On a default 64-bit operating system installation, with Windows on Windows 64 enabled, you can use 32-bit Aspnet_regiis.exe to configure IIS 7, but you will not be able to run any 32-bit applications, unless you explicitly change the enable32BitAppOnWin64 attribute to enable running the application in Windows on Windows 64. For more information about IIS 7.0 configuration options, see the documentation for the applicationPools element in the Applicationhost.config file.

So far I've also had success in running 32-bit web applications by using the method you described in your question.