When trying to launch the client on one of my older systems, I get an error message about a missing procedure entry point named freeaddrinfo in WS2_32.dll.
After some searching, it seems the devs need to add two more files to the source. It seems to be pretty simple.
The freeaddrinfo function was added to the Ws2_32.dll on Windows XP and later. To execute an application using this function on earlier versions of Windows (Windows 2000, Windows NT, and Windows Me/98/95), then you must include the Ws2tcpip.h file and also include the Wspiapi.h file. When the Wspiapi.h include file is added, the freeaddrinfo function is defined to the WspiapiFreeAddrInfo inline function in the Wspiapi.h file. At runtime, the WspiapiFreeAddrInfo function is implemented in such a way that if the Ws2_32.dll or the Wship6.dll (the file containing freeaddrinfo in the IPv6 Technology Preview for Windows 2000) does not include freeaddrinfo, then a version of freeaddrinfo is implemented inline based on code in the Wspiapi.h header file. This inline code will be used on older Windows platforms that do not natively support the freeaddrinfo function.
Source:
http://msdn.microsoft.com/en-us/library/ms737931(v=vs.85).aspx
