I found the constant for the "Program Files (x86)" folder. It is &H2A&. Tested on Windows Server 2008 R2 (64-bit) and on 32-bit Vista (where it returns the "Program Files" folder). On Windows 2000 and XP the resulting folder object is Nothing.
The script was tested and works on 32-bit Vista and on Windows Server 2008 R2 (which is 64-bit). The question is, how do you determine the (x86) folder name, Program Files (x86)? Indeed, how do you tell for sure if the OS is 32 or 64-bit?