fvwm-crystal.play-movies: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/bin/fvwm-crystal.play-movies - from package: fvwm-crystal

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