gnome-screensaver-preferences: 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/gnome-screensaver-preferences - from package: gnome-screensaver

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

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