NiConvertXToONI: 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/NiConvertXToONI - from package: openni-examples

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

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