Yeah, I really don't know why Net-SNMP doesn't distribute prebuilt binaries with their code. It's bizarre.
Anyways, I recently built 5.7.3 for Windows 64-bit (with full support for SSL, IPv6, and SNMP extension DLLs). You can download the binaries here: http://www.mediafire.com/download/5b6xs5u3lajl3s2/net-snmp-windows-x64-5.7.3.7z
Because I compiled this with Visual Studio 2015, you will also have to install the Visual C++ Redistributable for Visual Studio 2015 from here: https://www.microsoft.com/en-us/download/details.aspx?id=48145
Unzip the archive to C:\Program Files\Net-SNMP. You should be able to run the bin\snmpd.exe file to launch the agent. Edit etc\snmp\snmpd.conf (or run bin\snmpconf) to configure the agent. You can run:
snmpd.exe -register <add arguments to snmp.exe here>
to install the agent as a Windows service. Remember to add an exception to your Windows firewall for the snmpd.exe executable. And that's how you install Net-SNMP for Windows x64.
I'll also provide you with the exact steps I used to compile the binaries, so at least this can be documented concisely somewhere on the Internet. The official documentation for how to do this is incredibly lengthy, erroneous, and outdated.
Prerequisites: Active Perl x64, Visual Studio Community Edition (I used 2015). Note that the version of Visual Studio you use will effect the paths used below in the compilation instructions, so modify the path below accordingly if you're using something other than the 2015 edition.
First, compile OpenSSL for Windows x64. Unzip the source code, and in the same directory:
call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" x64
perl Configure VC-WIN64A --prefix=C:\OpenSSL-Win64
ms\do_win64a
nmake -f ms\nt.mak
nmake -f ms\nt.mak install
move C:\OpenSSL-Win64\lib\libeay32.lib C:\OpenSSL-Win64\lib\libeay32MD.lib
That last step renames the OpenSSL static library to something that Net-SNMP expects.
Now, compile Net-SNMP. Unzip the source code, and in the win32 directory:
call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" x64
set Platform=x64
set TARGET_CPU=x64
set INCLUDE=%INCLUDE%;C:\OpenSSL-Win64\include
set LIB=%LIB%;C:\OpenSSL-Win64\lib
perl Configure --with-sdk --with-winextdll --with-ssl --with-ipv6 --config=release --linktype=static --prefix="c:/Program Files/Net-SNMP"
manual step: edit net-snmp\net-snmp-config.h, comment out #define snprintf (this is fixed in their git repository)
nmake clean
nmake
nmake install
One you've installed Net-SNMP, you can uninstall and delete everything else just fine (Active Perl, Visual Studio, OpenSSL, etc.) and Net-SNMP will still work. Obviously make sure you keep the VC++ redistributable installed.
I hope this helps somebody out there.