WOW64 is a subsystem of the Windows operating system that enables 32 bit Windows-based applications to run on 64 bit Windows. Wow64.dll, the core interface to the Windows NT kernel that translates between 32-bit and 64-bit calls. This is used in x86-64 implementations of Windows only.

The 'Program Files (x86)' and 'SysWOW64' folders explained / Windows 64-bit (Technical Article) Windows 64-bit: The 'Program Files (x86)' and 'SysWOW64' folders explained If you use a 64-bit computer with a 64-bit Windows installed (for example the 64-bit version of Windows 7) you have probably discovered that there are two new folders with the names Program Files (x86) and SysWOW64 on the hard disk, that do not exist on a 32-bit Windows. Maybe you have wondered what these folders are, why they exist and what kind of files they contain? In this article we will explain these folders and also explain why it is important to place with files with a specific bitness (32 or 64 bit) in the right folder on the hard disk. Advertisement 32-bit versus 64-bit computers and Windows Since the mid-90s almost all computers that have been sold have been 32-bit computers, and mostly they have had a 32-bit Windows installed.

But after the release of Windows 7, the sales of 64-bit computers with a 64-bit Windows installed have increased a lot. In the coming years, more and more people will have a 64-bit computer with a 64-bit Windows in their home or office. One reason to this is that the price of a 64-bit computer have decreased so much that they are almost as cheap as 32-bit computers. And people will prefer 64-bit computers over 32-bit computers because they can handle much more (RAM) memory and they are generally faster because they use more modern technology. A 32-bit computer with a 32-bit Windows installed can use a maximum of 3 to 4 GB (RAM) memory. Mostly around 3 GB because a large part of the address space is used by video cards and other devices such as network cards, sound cards etc. This is true even if you install 4 GB in the computer.

Mostly only around 3 GB RAM will still be used. With 64-bit computers and 64-bit Windows things are different. A 64-bit computer with a 64-bit Windows can handle so much RAM memory as 192 GB! On a 64-bit Windows, both 32-bit and 64-bit programs can be run Both 32-bit and 64-bit programs can be run on a 64-bit Windows.

When a 32-bit program is run on a 64-bit Windows, a 32-bit emulator will be invoked to handle the 32-bit program. The emulator will make the 32-bit application to think it is running on a 32-bit Windows and the same functionality that is accessible on a 32-bit Windows will also be accessible for the program on the 64-bit Windows. Normally it will be hard for the program to know if it is running on a 32-bit or 64-bit system, but if the program really needs to know the difference there are API functions available that the program can call if needed. Exceptions: Antivirus programs etc There are a few exceptions from this. 32-bit programs that function at low level, such as antivirus programs, will not always work on a 64-bit Windows; then a 64-bit version of the program must be used. During the installation, it is important to install files into correct folders As mentioned above the 32-bit emulator handles the situations when 32-bit programs are run on a 64-bit Windows and normally this works fine.

But one sensitive phase is the installation of the 32-bit program. There exists special folders on the hard disk that is intended for 32-bit binary files only and it is very important that the installation program installs the 32-bit binary files to these folders. Some folders on the hard disk are intended for 32-bit binary files only and other folders are intended for 64-bit binary files only. If you place binary file with a specific bitness (32/64 bit) in a folder intended for another bitness the program will probably fail to work properly; in many cases the program will not even start. Examples of binary files that is mentioned in this article are EXE files (program files), DLL files and OCX files (ActiveX components). Data files can usually placed in same folders and shared by both a 32 and 64 bit application. T wo different versions of the Program Files folder and the Windows System folder A 64-bit Windows has two different versions of the program files folder and the Windows system folder (system directory).

One version is intended for 32-bit files and other version is intended for 64-bit files. The name of these folders, and the bitness they are intended for, is shown in the table below: Folder name Bitness Description System32 64 Windows System folder (system directory) for 64-bit files SysWOW64 32 Windows System folder (system directory) for 32-bit files Program Files 64 Folder for 64-bit program files Program Files (x86) 32 Folder for 32-bit program files Below you can see the full path to the folders.