hpitop: 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/bin/hpitop - from package: openhpi32
/usr/bin/hpitop - from package: openhpi

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

On Debian possible default full paths are:

/usr/bin/hpitop - from package: openhpi-clients

You may install the required package with command apt-get install {package}

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