More and more users switch to x64 Windows operating systems and support
requests similar to the following are under our top 10 FAQs now:

QUESTION:

> I'm working on adding a couple of dlls from the development
> computer to the destination computer and I'm adding the two
> dlls in the System32 folder (they have to be in that specific
> folder). I just navigate to the System32 folder in the bottom
> left panel and I select my dlls from the destination computer
> and click add. After I compile and install it on my target
> machine, the dlls automatically go in the SysWOW64 not the
> System32. Any idea why that's happening?

ANSWER:

On Windows x64 systems, 32-bit DLLs always go into the SysWow64 folder.
Only native 64-bit DLLs have to be installed to System32 on x64 systems
(when running the setup in x64 mode).

SetupBuilder lets you build installations for 32-bit and both pure 64-bit
applications and hybrid applications that mix 32-bit and 64-bit code.

[Taken from the SetupBuilder manual]

Not long ago, 64-bit systems were a future technology reserved almost
exclusively for high-end enterprise implementations. The widespread adoption
of the 64-bit capabilities for x86 architecture (referred to as x64) by both
computer manufacturers and Microsoft, however, dramatically changed the
computing landscape. Now, 64-bit systems are a reality for both high-end
enterprise systems and small-to-midsized businesses (SMBs). 64-bit computing
is moving into the mainstream and will gradually replace 32-bit computing.
Microsoft foresees significant adoption of 64-bit-capable systems.

WOW64, short for "Windows-32-on-Windows-64," is responsible for providing
two levels of support for 32-bit legacy applications. WOW64 prevents file
and registry collisions between 32-bit and 64-bit versions of applications
by redirecting the 32-bit registry and file system accesses.

SetupBuilder Developer Edition lets you create native 32-bit, hybrid
32/64-bit, or 64-bit enabled setup programs.

Although the WOW64 subsystem doesn't support every type of application, it
does let Windows x64 run almost all 32-bit existing Windows applications.
The types of applications that aren't supported are low-level applications
such as antivirus programs or programs that attempt to directly access
system hardware. The 32-bit applications that run in the WOW64 subsystem are
executed at full speed. In fact, because of the larger data path the x64
architecture provides, many 32-bit applications will actually run faster in
the WOW64 subsystem than they would on native 32-bit hardware.

The WOW64 subsystem isolates the execution of 32-bit applications from
64-bit applications.

First, the system files in Windows x64 Edition are not present on just the
Windows\System32 folder, but split into two folders to separate the 32-bit
applications from the 64-bit applications. The WOW64 subsystem intercepts
calls from a 32-bit legacy application and redirects it to the
Windows\SysWow64 folder. If the call is from a 64-bit application, then the
call is routed to the Windows\System32 folder and does not involve the
WOW64. Microsoft has retained the name System32 for the folder, which hosts
the 64-bit system files. The "Program Files" folder on a x64 system which
stores 32-bit legacy applications is named Program Files (x86). 64-bit
applications are stored in the Program Files folder.

Second, the WOW64 subsystem also provides redirection at the Registry level.
Computers that are running an Windows x64-based operating system use a
different registry layout to handle both 32-bit and 64-bit programs. The
registry layout changes in x64 Edition versions of the Windows operating
system make sure that the programs hard-coded .dll paths, program settings,
and other parameter values are not overwritten. If the call is from a 32-bit
application, then the call to access the HKLM\Software registry hive is
intercepted by the WOW64 subsystem and redirected to the
HKLM\Software\Wow6432Node. If the call is from a 64-bit application, then it
is routed to the HKLM\ Software node.


-- Registry Redirection

To prevent 32-bit registry settings from overwriting the 64-bit registry
settings, computers that are running an x64-based version of Windows store
the settings for 32-bit programs in a new branch in the registry.

32-bit programs and 64-bit programs that are running on an x64-based version
of Windows operate in different modes and use the following sections in the
registry:

* Native mode 64-bit programs run in Native mode and access keys and values
that are stored in the following registry sub key:

HKEY_LOCAL_MACHINE\Software

* 32-bit programs run in WOW64 mode and access keys and values that are
stored in the following registry sub key:

HKEY_LOCAL_MACHINE\Software\WOW6432node

This redirection lets you maintain separate configurations for 32-bit and
64-bit processes. 64-bit programs see the 64-bit version of the registry,
while 32-bit programs see the 32-bit version.


-- File System Redirection

All 32-bit file access to the %systemroot%\system32 folder is redirected to
the %systemroot%\syswow64 folder (the %systemroot%\syswow64 that contains a
copy of 32-bit Windows system executable programs). This redirection lets a
32-bit applications load the correct 32-bit system executables rather than
attempting to access the 64-bit OS executable programs.


Friedrich

--
Friedrich Linder
Lindersoft
www.lindersoft.com
+1.954.252.3910

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