How To Switch 32-bit and 64-bit mode in IIS 7.x (Windows Server 2008 x64)?

Problem:

On a 64 bit Windows 2003 machine IIS 6.0 could either be run in 32 bit mode or 64 bit mode. You toggled the Enable32bitAppOnWin64 metabase key and all the worker process would run in a particular bitness mode.

With IIS 7.0 the Enable32bitAppOnWin64 key has been moved to the Application Pool level. So you can now set the bitness of a particular Application Pool.

Solution:

You can set the application bool bitness via the IIS manager.

Step 1) Open IIS Manager

Click Start -> Administrative Tools -> Internet Information Service (IIS) Manager

Step 2) Go To Advanced Settings of application Pool

Go to Application Pool control panel, Right click the Application Pool name and select 'Advanced Settings...'.

Step 3) Enable 32 Bit Applications.