About ntvdm.exe

ntvdm.exe is part of the Windows 16-bit virtual machine. This process is used to allow 16-bit processes to run in a 32-bit system environment. This program is crucial for the proper functioning of your system.

What does this mean?

As is widely known, Microsoft's new desktop operating systems are backward compatible. For example, you can run PE format executable files designed for DOS-based operating systems on Windows XP, as well as games developed for DOS (excluding those that attempt to directly access hardware, as it exceeds the permissions provided by the NT kernel operating system to applications, or they attempt to run at the R0 level of the processor, which is the same level as the operating system kernel. This is obviously not allowed for the security of the kernel).

Microsoft adopted the WOW (Windows On Windows) technology, which allows applications developed for older operating systems to run on newer ones like Windows XP with the NT kernel. This enables us to run programs such as the Windows 98 calculator or even Windows 3.2 calculator smoothly. When we open Windows 3.2 applications (like Notepad) on Windows XP, you will notice the appearance of the NTVDM program, accompanied by a subprocess called WOWEXEC.exe. This is an example of the WOW technology in action.

For 16-bit programs developed for DOS, which operate in real mode on the CPU, Microsoft uses the method of a DOS virtual machine (VM). NTVDM employs the virtual 8086 mode of x86 CPUs, allowing 16-bit programs to run within certain permission boundaries unless they attempt to directly access hardware, as explained above. If you open HD-copy on XP, you will see ntvdm.exe popping up again.