xfterm4: 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/xfterm4 - from package: xfce-utils

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

Error in other languages:
xfterm4: bevel nie gevind nie
xfterm4: comandă negăsită
xfterm4: comando não encontrado
xfterm4: commande introuvable
xfterm4: command not found
xfterm4: käsku ei ole
xfterm4: không tìm thấy lệnh
xfterm4: komanda nerasta
xfterm4: Kommando nicht gefunden.
xfterm4: kommandot finns inte
xfterm4: komut yok
xfterm4: nie znaleziono polecenia
xfterm4: níor aimsíodh an t-ordú
xfterm4: no se encontró la orden
xfterm4: no s'ha trobat l'ordre
xfterm4: opdracht niet gevonden
xfterm4: parancs nem található
xfterm4: perintah tidak ditemukan
xfterm4: príkaz nenájdený
xfterm4: příkaz nenalezen
xfterm4: команда не найдена
xfterm4: командата не е открита
xfterm4: 命令找不到
xfterm4: コマンドが見つかりません