Windows NT-based computers use the Virtual DOS Machine (NTVDM) to run MS-DOS and 16-bit Windows applications.

If you receive the following,  your only option is to press OK:

NTVDM.EXE has generated errors and will be closed by Windows.
You will need to restart the program.

An error log is being created.

Virtual-8086 mode is used to run MS-DOS and 16-bit applications in their own environment, without interfering with other applications. Most modern processors have support for Virtual Mode Extensions (VME), which provides enhancements to virtual 8086 mode, but it is possible that your processor may not have full support for VME.

NTVDM.EXE has code to support non-VME processors, but it has not / will never be fully tested.

If you processor is not fully VME compliant, certain combinations of hardware, drivers, memory, and application usage may exhibit this behavior.

NOTE: See the following related tips:

How do I troubleshoot 16-Bit Windows programs in Windows XP and Windows 2000?

Troubleshooting NTVDM and WOW startup problems.

Hidden Autoexec.bat and Config.sys files prevent 16-bit MS-DOS programs from installing?

Error when you run or install an MS-DOS or 16-bit Windows program on Windows XP?

Your 16-bit program stops responding on Windows 2000?

How do I identify 16-bit programs?

How do I troubleshoot MS-DOS programs running on Windows XP?