ntfsdecrypt: 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:

/bin/ntfsdecrypt - from package: ntfsprogs
/usr/bin/ntfsdecrypt - from package: ntfsprogs

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

On Debian possible default full paths are:

/usr/bin/ntfsdecrypt - from package: ntfs-3g

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

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