Vista Files Security problem

Hello guys,

I'm new here, so sorry if this topic doen't belong here... My apologies...

I copied some songs and pictures form my friend's computer, and now when I want to start a song on my computer, I can't.

Winamp and WMP are having the same error (it's not an error but they wont play the song). I searched in file's properties and found under security tab account that isn't there; only some letter and numbers (S-1-5005-33...).
I added another user account (my account), set up full control permissions and when I pressed apply, old account was gone, only mine stayed. After that I can use that file, I mean I can listen to the song.

But do I need to do that procedure on every single file ? Or is there some Windows command to remove that user from registry files or some program ?

Btw I use Win Vista Ultimate, as my friend too.

Thanks,

Regard