5.1.2600 is the command version. Try typing: "ping /?" if you get an error similiar to the below example.
'ping' is not recognized as an internal or external command,
operable program or batch file.
It's likely the command has been disabled as part as your setup since it should be part of the default install for Windows. If you're on a school computer or work computer, it's likely the admin has disabled it.