windowlab: 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/windowlab - from package: windowlab

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

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