ehm... you do know that you have to execute this commands as root, don't you?

so you have to type "sudo gainroot" first...
but you should have noticed that already. ^^
(from reading all along this thread)

i don't understand what you mean with:
"I now have around 7 'wave symbol'media folder with 7 avi files inside usr/share/hildon-welcome/media" ??? o.O