openbox-lxde: 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/bin/openbox-lxde - from package: lxde-common

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

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