I was finally able to convert a Youtube video so it would work in Powerpoint 2003 on my computer. There are all kinds of places that "say" they can do it, but for some reason none of them worked for me. But I finally stumbled onto Zamzar, and after a few tries, got the job done. I was converting an flv file, and I had to convert it to an mpg file before it would work. I tried mp4, and avi, but neither of them worked correctly on my version of Powerpoint. So I am glad to have that over with.
I didn't actually join or register with Zamzar, but put the thingy on my browser bar, and when I go to the youtube video I want, I click on the Zamzar thing, and then select the format, put my email address in (I've never received any junk mail from them), and convert. Pretty soon they email me the place to download from, I download it, and presto/chango... it works! Cool.