dpconv: 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/sbin/dpconv - from package: dpsearch

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

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