Ehm, nope... Programs made for rev 20 might behave funny if running with rev 40. (etc etc)

These are excerpts from the MS Knowledge Base found on:
http://www.microsoft.com/kb/articles/q94/2/48.htm and
http://www.microsoft.com/kb/articles/q28/1/73.htm 

Microsoft Visual C++ 32-Visual C++ 32-bit Edition, versions 2.x and 4.0

The CRT libraries provided are identical to those provided in Visual C++ 32- bit Edition 1.0. However, the import library MSVCRT.LIB now refers to the DLL MSVCRT20.DLL for Visual C++ 2.x and either MSVRCT40.DLL or MSVCR40D.DLL for Visual C++ 4.0. MSVCR40D.DLL is a debug version of the DLL for Windows NT and Windows 95 (Win32). In addition, with Visual C++ 2.1 and above, there are two versions of MSVCRTx0.DLL: one that targets Win32 and the other that targets Win32s. bit edition contains these three forms as well, however, the CRT in a DLL is named MSVCRT.LIB. The DLL is redistributable. Its name depends on the version of VC++ (ie MSVCRT10.DLL or MSVCRT20.DLL). Note however, that MSVCRT10.DLL is not supported on Win32s, while CRTDLL.LIB is supported on Win32s. MSVCRT20.DLL comes in two versions: one for Windows NT and the other for Win32s.

Hope this helps...

From 4.00.950 System
ALL IN /SYSTEM
MSVCRT.DLL ver 4.20.6201 8/2/96
MSVCRT20.DLL ver 2.11.000 7/11/95 ON WIN95 CD-ROM
MSVCRT40.DLL ver 4.20 - OS use only. DO NOT DISTRIBUTE 8/2/96

My question is still not answered.

When one installs Windows NT 4.0, Windows NT 3.51, Windows95 which of following Dlls get installed on users machine?
MSVCRT.DLL
MSVCRT20.DLL
MSVCRT40.DLL

My application is compiled and linked with runtime libraries
(So if I compile on MSVC 2.0   --- it needs msvcrt20.dll
        if I compile on MSVC 4.0   --- it needs msvcrt.dll and msvcrt40.dll)
So to run my application do I need to carry particular Dlls with my application?
Can I assume that any one of above dlls like MSVCRT20.dll will always be present on NT3.51, NT4.0, Win95 ?