Solved: Ping not recognized as internal or external command

My guess is your computer's Path statement got messed up.
To check it open a Command Prompt and type: Set <hit Enter>

You should see included:

Path C:\WINDOWS\system32

To edit the Path to correct it select
Start>>right click My Computer>>select Properties>>Next select the Advance tab>> Environment Variables>>select the Path variaible listed under System Variables

When editing it should include:

%SystemRoot%\system32;

Which translates to something like:

C:\WINDOWS\system32

Each entry included in the path must be separated by a semicolon.
Good luck.

source : http://forums.techguy.org/windows-xp/420462-solved-ping-not-recognized-internal.html