the electrum program folder isn't in your path... This basically means you have to open a command prompt and go to the correct folder where electrum.exe is located, only then you can execute the command (or maybe the electrum binary isn't electrum.exe but electrum-2.x.x.exe... In this case you need to execute electrum-2.x.x instead of electrum).
Since i use the portable version, i don't know where this folder is located, but it's probably something like c:\program files\electrum\

The point is moot tough... Like many have already suggested, it seems like cli arguments were removed, i just tried some of the arguments i found here; http://docs.electrum.org/en/latest/cmdline.html on electrum 2.7.8 portable on windows 7, and nothing happened. I could try this on my linux distro when i get home in case somebody is interested.