How can you download Youtube videos to your PSP? PLEASE ANSWER!!!!!!!!!?

Here's my story: I download videos to my PSP using PSP Video Express (I use this for videos I get off of Ares). I recently tried downloading videos using Google Video Help Center and everytime I put my favorite video into the folder, it comes up as Corrupted Data. I tried the thing that you copy and paste your URL from youtube into the box, but it starts to get complicated and I can't convert it. What am I doing wrong? Please I'll give best answer to the user that can get me an easy. detailed response that works.