sampasswd: 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 Debian possible default full paths are:

/usr/sbin/sampasswd - from package: chntpw

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

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