laurilli, it looks like Bonnie has removed the Easy Angle and Companion Angle videos from her blog, I suppose because she is promoting her own tool, which I think it is called the Essential Triangle Tool. Maybe that would be the best one for you to buy, since she will be teaching how to use it during the mystery, and it does the same things as those other two. If you want to look into the Easy Angle and Companion Angle, I would suggest googling 'how to use easy angle ruler,' and I bet there will be YouTube videos showing how they work.
But as for why the videos on Bonnie's blog show black to you and aren't playable, I don't know what to suggest. Sometimes that happens to me at various websites, but I'm afraid I am also pretty clueless when it comes to computers!