Probably no need to explain that many users often see a message on the monitor screen at the most inopportune moment that some executable file is not a Win32 application. Let's see what Win32 is and why architecture or file system errors occur. By considering these two questions, it will be possible to find a solution to the problem of non-compliance of the application with this standard.
What is Win32
If we talk about the concept as a whole, it is usually referred to the architecture of the "OS" and the applications supported in it to start and work.

From the history of the creation of operating systems, it is known that at first they were 8- and 16-bit, a little later they were transformed into 32-bit and, finally, into 64-bit. Along with the evolution of the principles of operation of the operating systems themselves, file systems have also changed. Until recently, the FAT32 file system was considered the most common. She wonsuch popularity that until now the developers of the IT giant Microsoft do not exclude its support in the latest versions of Windows.

By the way, the concept of what Win32 is is equally applicable to "OSes" such as XP and Vista, because even with the NTFS file system that replaced FAT32, the versions of the OS themselves in terms of architecture remained 32-bit.
With the advent of Windows 7, a transition to 64-bit architecture was made, however, for a custom installation, you can also find a 32-bit version of any of the four assemblies of the "seven".
Why errors happen
Now let's look at the question of concern to everyone, what is "Not a Win32 application" (such and such an installation or executable component). Firstly, the simplest reason is the file itself, created, for example, in Linux or Mac OS X, which, of course, is simply not recognized in all Windows systems due to the fact that the “OS”, so to speak, does not know what this is for the component and how to open it. Very often, such situations can be observed when working with disk images such as.dmg or some archived data.

On the other hand, errors can also occur with "native" Windows applications. When answering the question of what a Win32 application is, it is worth noting that it is a program, dynamic library, or driver that was originally created using the 32-bit architecture. Now, probably, it is clear that a 64-bit application or a driver in a 32-bitsystem will not work.
There are fewer errors when opening executable files or archives. Here the problem may be that the file was not downloaded (copied) in its entirety, or failures occurred. In this case, the system can also issue a message about the format or type of the file being opened does not match the requirements of the system itself.
Simple troubleshooting techniques
However, there are many ways to troubleshoot such problems. The simplest solution can be to download a specialized Win32.reg file from the Internet and then run it.
What is Win32.reg? This is a system registry file that adds specific entries and keys to it to simplify the process of opening problematic applications.
Sometimes the situation can be related to mismatch of file systems. In this case, you will need to format the disk or partition using, for example, FAT32 (especially when switching from a 64-bit OS to a 32-bit one).

There are situations when an update of the Microsoft. NET Framework is required, where in the platform settings you need to specify support for absolutely all processors, including x86. In general, there are quite a lot of examples.
If it's a virus
The worst case of failures of this nature is the impact of viruses and malicious codes that disguise themselves as system services responsible for launching or calling 32-bit applications like rundll32, svchost, etc.

Let's consider one of the most famous threats. What is Trojan:Win32 (Gatak or some other modification)? Yes, a common computer virus (Trojan) that, using security holes, tries to gain access to a remote user's computer in order to steal information or gain complete control over a computer terminal.
Here, you definitely need to have a high-quality regular antivirus or the most powerful system scan tool in the form of a scanner (for example, Kaspersky Virus Removal Tool or Rescue Disc) at your disposal, since sometimes it is not possible to track the appearance of a threat in the system using standard methods.
Conclusion
Here, actually, albeit briefly, we have considered the question of what Win32 is. Of course, the information is presented in a compressed form, however, an ordinary user does not need to climb into the jungle of programming and understanding the principles of using the architecture of the "OS" or the file system. In extreme cases, it is enough to find out the problem of errors and choose a method for eliminating them.