The commands that are working are all (I'm pretty sure) commands internal to the command processor, whereas the ones that aren't working are all external programs. So either those programs are missing (unlikely) or your PATH variable isn't set correctly.
dir c:\windows\ping.exe /s
to check the former (it should find the program in c:\windows\system32) and
to check the latter (the path should include the directory c:\windows\system32).
If the PATH variable is wrong you can edit it as shown in this article.