Follow these steps:
1. Place the student's presenation in the same folder as yours
2. Change the file extension of the student's presentation to *.pps (most
are *.ppt when created)
3. Open your presentation and insert some sort of object on the desired
slide that you can click on (I usually use the Custom Action Button under
"Autoshapes/Action Buttons" on the Drawing Toolbar. Set the Action Setting
to "Hyperlink to" "Other PowerPoint presentation", browse to and select the
other file. Select what slide to start on (usually the first slide).
You're ready to go!