cpuspeed: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/sbin/cpuspeed - from package: cpuspeed

You may install the required package with command yum install {package}

Error in other languages:
cpuspeed: bevel nie gevind nie
cpuspeed: comandă negăsită
cpuspeed: comando não encontrado
cpuspeed: commande introuvable
cpuspeed: command not found
cpuspeed: käsku ei ole
cpuspeed: không tìm thấy lệnh
cpuspeed: komanda nerasta
cpuspeed: Kommando nicht gefunden.
cpuspeed: kommandot finns inte
cpuspeed: komut yok
cpuspeed: nie znaleziono polecenia
cpuspeed: níor aimsíodh an t-ordú
cpuspeed: no se encontró la orden
cpuspeed: no s'ha trobat l'ordre
cpuspeed: opdracht niet gevonden
cpuspeed: parancs nem található
cpuspeed: perintah tidak ditemukan
cpuspeed: príkaz nenájdený
cpuspeed: příkaz nenalezen
cpuspeed: команда не найдена
cpuspeed: командата не е открита
cpuspeed: 命令找不到
cpuspeed: コマンドが見つかりません