Does any command work from the command prompt? Are you entering cmd or command to get there?
It with out knowing more information, try changing to the system32 sub directory under windows [windows or winnt] and try running the commands for their native directory. If they run from there, then your path statement which can be found from system properties, advanced, enviromental variables, system variables is usually messed up causing this problem.
Let us know more information, like can you run notepad from your command prompt or is it just network commands.