Time for me to play the computer numpty...

If someone sends me a link to a youtube vid, it plays fine with all sound...supa di dupa!!

If I go to youtube and try to play the same link, I don't get any sound...hmmm!!

All abuse accepted in the manner it's delivered, but it's puzzlin' me and affecting my sleep at night..!!!

It's not really, but an explanation would be much appreciated.