How to "Downgrade" to Adobe Flex SDK 4.1 (AIR 2.0) in Flash Builder 4.5

Intel AppUp Application Store does not yet accept Adobe AIR 2.6 / Flex 4.5 desktop applications (at least this is true as of 8 August 2011) because the Adobe InMarket SDK supports only up to AIR Runtime 2.5.

Here's how to "downgrade" the Adobe AIR SDK (actually, install an older version of Flex/AIR SDK) in Adobe Flash Builder 4.5:

1. Download Adobe Flex SDK here. Choose Adobe Flex SDK 4.1.
2. Extract the downloaded SDK somewhere in your User home folder.
3. In Flash Builder, click Window menu > Preferences.
   Navigate to Flash Builder > Installed Flex SDKs.
4. Click Add... button then locate your old Flex SDK.

Now you need to configure your project to use the older Flex SDK.
Right-click your Flex project, navigate to Flex Compiler.
Then select the older Adobe Flex SDK version (Flex 4.1).

Now your AIR application should run with the InMarket SDK and can be successfully published to Intel AppUp application distribution channel.

To learn more on Adobe Flash/Flex/AIR applications development, get Flex 4 Cookbook.