Can't ping Windows 7 from Android phone and vice versa in the same network, but other machines can
Are you using a Samsung Android running Lolipop? It is actually locked down and some Chinese hackers actually created the PINGPONG root to enable pinging from a Samsung Android.

http://forum.xda-developers.com/galaxy-s6/general/root-pingpongroot-s6-root-tool-t3103016