gtk-window-decorator: 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/gtk-window-decorator - from package: compiz-gnome

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

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