I am a high school teacher. I have assigned projects using PowerPoint. I have created many PowerPoint projects myself. Recently, there have been two problems that I cannot resolve. I need help.

Project #1) On one particular project, there is an mp3 file. It plays on my desktop. When I attempt to play it on the laptop, there is silence. When I left-click on the icon, I get the following message: "MMSYSTEM296 The file cannot be played on the specified MCI device. The file may be corrupt, or not in the correct format."
However, if I convert that same file to WAV, it plays on the laptop. If I attempt to play that same file out of PowerPoint, it plays on the laptop. If I try to insert other mp3 files into that same presentation, most of the times they play. On one occasion I got an error message saying, "PowerPoint couldn't insert a sound from the selected file." Could it be that there are some mp3 files that PowerPoint will not accept on some computers?

Project #2) Student submitted a project of 147 mb. He told me that he could not insert mp3 files. Instead, he put wav files. However, the presentation (on my desktop) shows no indication of any sound files. No icons, no sounds. What would make a file size of 147mb without sounds? (There is no video.) He claims he did use Pack and Go. He sent me the mp3 files. I was able to insert the mp3 files into his presentation. I would like to remove the wav files but I can't find the wav files to remove! If it means anything, let me bring out the following information about this presentation:
1) It will not open up on my desktop from the CD. When I copy the files to hard drive, it does open up. It will not open up on my laptop. It opens up slowly on the student's computer.
2) The student claims he did use Pack and Go but it made his computer freeze.

I would appreciate any help/information that anyone would have.
Thank you very much.
Alan Silberlight