PowerPoint

I don't know what is going on with my PowerPoint presentation. I downloaded Microsoft Office 2007 onto my laptop and my desktop from the same CD, yet they don't seem to have the same fonts. I created the presentation on my laptop and saved it on a flash drive. When I opened it on my desktop, most of the fonts had changed and some of the text moved out of the position I put it in. I don't know what to do about this. How I am supposed to know what it is going to look like if it keeps changing on its own?