dvdtguess: 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/dvdtguess - from package: dvdwizard

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

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