Internet Exporer 8.0 and 7.0

other version might also work.

1) Go to Tools and chose Internet Options

2) In Internet options go to the "Privacy" Tab and in settingclick on the button "sites"

3) Then a window Per Site Privacy Actions will appear and in the blank space type "www.youtube.com" and then click on the button block finally, click on OK.

or

You can go to the "Privacy" Tab under setting raise the level to High and then click OK

If you have an account the down side of this is that you wont be able to sign into your account so make sure that you are sign in first. To be able to sign in you just have to remove the youtube website from the blocked list. It is up to you if you want to deal with this Bar on the bottom.