Hiding Your Server From Enumeration

If you don't want your server to be displayed in Network Neighborhood, add a registry value [HKLM \SYSTEM \CurrentControlSet \Services \LanmanServer \Parameters \Hidden]. Make Hidden a DWORD, with value "00000001". This will prevent it from reporting any shares to the browser.

Conversely, if your server isn't showing up in Network Neighborhood, and you want it to show up there, check for that value. If it exists, make sure that it has a value of "00000000", or delete it altogether.