putty: 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/putty - from package: putty

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

On Debian possible default full paths are:

/usr/bin/putty - from package: putty

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

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