Running 16-Bit and MS-DOS Applications

Windows XP has the capability to run old 16-bit applications and MS-DOS applications (which are also 16-bit applications) that were originally developed for Windows 3.x. Basically, all programs sold today are 32-bit applications. However, your environment may have a custom application that was developed years ago that management still wants to use on Windows XP. To run 16-bit applications, Windows XP starts a virtual machine, which is a subsystem designed to mimic the Windows 3.x environment so that these applications can run. The subsystem places the 16-bit application in its own virtual machine, or memory space, so that the application theoretically can run without interfering with other applications on Windows XP.

If you need to use a 16-bit application, keep in mind that most do not support long filenames and most will not run as fast as 32-bit applications, due to the translation process necessary to make the programs run under Windows XP. Also, some 16-bit applications simply do not run well under Windows XP because of the way they try to access hardware. So, keeping in mind all of these caveats, Windows XP can run most 16-bit applications using the virtual machine. When you run several 16-bit applications, Windows XP places each in its own virtual machine, so that the 16-bit applications cannot interfere with each other. Keep in mind, however, that virtual machines consume more system resources, so try to keep their use to a minimum.

Note 

If you are not sure whether an application is a 16-bit application or not, open Task Manager and inspect the executable on the Processes tab. You’ll see an entry for NTVDM.exe in the Image Name column. You’ll also see the Wowexec.exe processes running; this executable is the virtual machine.