Dynamics AX 2009 fails to install because of WOW64 registry setting in Windows Installer

Part 1: 

When the value of the WOW64 is set to 1 it fools the installer to think that the OS is 32 bit. This is helpful in running installers that are not compatible with 64bit OS. However, most of the 32bit installers are compatible with 64bit OS and do not need this value set to 1. When the value of WOW64 is set to 0 it returns the actual OS architecture to the installer. That is if it is 32 bit then the installer will come to know its a 32 bit OS, similarly its true for 64bit OS.

1. Set the value of WOW64 to 0 under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\msiserver

2. Restart the Windows Installer service

Part 2: 

When the AX 2009 install fails with this error, it also fails to roll back (probably also because of the WOW64 key). Retrying the install after removing the WOW64 key may result in the following error:  "An unexpected exception occurred during Setup.  See the log file … for details."

The log shows the following details:

Performing  prerequisite validation: DhtmlEd

Exception: System.ArgumentException

Message: Unknown property.

FullText: System.ArgumentException: Unknown property.

   at Microsoft.WindowsInstaller.Installer.ProductInfo(String productCode, InstallProperty productProperty)

   at Microsoft.Dynamics.Setup.Misc.IsDhtmlEdInstalled()

1. Go to Control Panel > Programs > Programs and Features.
2. Manually uninstall the following programs: "DHTML Editing Component",

3. Retry the AX 2009 install.

4. Note, if you cannot uninstall the application, you may have to remove the following two keys in the registry:
   1. HKEY_CLASSES_ROOT\Installer\UpgradeCodes\3310FED00A6E18A4983CB4EC9B4689DA (DHTML Editor)

5. If you get similar errors on the VC++ redistributables, here are the other keys:
   1. ...\AA5D9C68C00F12943B2F6CA09FE28244 (Visual C++ 2005 Redistributable)
   2. ..\41A387AA3A7A33D3590FA953D1350011 (Visual C++ 2008 Redistributables)

Part 3:

After removing the WOW64 key, the AX 2009 installer may also crash with another error in the log:

While Setup was determining which Microsoft Dynamics AX features are currently installed, an unexpected exception occurred. Review the error log for details.

Exception: System.FormatException

 Message: Index (zero based) must be greater than or equal to zero and less than the size of the argument list.

This is because of an orphaned key for Dynamics AX

1. Delete the following key from the registry: HKLM\Software\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Products\8EECD6EA80D612247A0798D7DB58DE46