Specifies the 64-bit processor architecture(s) on which Setup should install in 64-bit mode. If this directive is not specified or is blank, Setup will always install in 32-bit mode.

Normally, you should not change this directive from its default value unless your application contains native 64-bit binaries.

Be sure you have read the 64-bit Installation Limitations topic before setting this directive.

If your application runs only on 64-bit processor architectures, you should set ArchitecturesAllowed to the same value as this directive to prevent Setup from running on 32-bit Windows.

Setup can only run in 64-bit mode on versions of Windows that provide the API support Inno Setup requires (e.g. RegDeleteKeyEx). All x64 editions provide the necessary APIs, however Itanium editions prior to Windows Server 2003 SP1 do not. If the user is running an older Itanium version of Windows, Setup will display a message (MissingWOW64APIs) recommending that the user install a service pack, and exit.

See also:
ArchitecturesAllowed