! Hi
.It really useful to try to immigrate from 32bit assembly coding to 64bit coding, cause of multi-platforms support
:To achieve this task, you need to download MASM64 package from
http://www.masm32.com/download/install64.zip

And copy the following needed files from Visual Studio

**********************************************
Files that must be obtained from Microsoft and
.copied into the following directories
.Usually this is from a Visual Studio download
**********************************************

---------------
bin64 directory
---------------
cvtres.exe
dumpbin.exe
editbin.exe
lib.exe
link.exe
link.exe.config
ml64.exe
msobj140.dll
mspdb140.dll
mspdbcmf.exe
mspdbcore.dll
mspdbsrv.exe
mspdbst.dll
mspft140.dll
msvcdis140.dll
msvcp140.dll

-----------
In dir 1033
-----------
bscmakeui.dll
clui.dll
cvtresui.dll
linkui.dll
LocalESPCui.dll
mspdbcmfui.dll
mspft140ui.dll
pgort140ui.dll
pgoui.dll

:Now try to build this sample

ifndef _Win64
    include masm32rt.inc
else
    include masm64rt.inc
endif

 
.const
    CmdToExecute db "calc.exe", 0
 
.code
    start proc
        invoke WinExec, addr CmdToExecute, 0
        invoke ExitProcess, 0
        ret 0
    start endp
end