Why is this not working?

I have to make a power point for my L.A. cl on the Lion, the Witch and the Wardrobe. I have an HP computer and it doesn't have 2007 power point on it. So I used my sisters computer which does. Its her school computer and Im not sure what brand. (And i know that is bad not to know) I think its like something like a CP in cursive? So yesterday I started my powerpoint and I put it on a flash drive to work on at school. And all the school computers are MAC. It wouldnt work and it didnt play any of the media I had. But when I tried it on my HP with the flash drive it played it on power point viewer. Why is this? Is it just becuase of the computer type? Will it work on a DELL?