From Powerpoint XP Help files:
About packaging a presentation to run on another computer.
When you want to run a presentation on another computer, use the Pack and Go Wizard to put all the required files into one file and copy the file to a disk or network location. You then unpackage the file onto the destination computer or network and run the presentation.
When you package your presentation, you can include any linked files in the package, and if you use TrueType fonts you can embed them as well. Embedding fonts guarantees that the fonts will be available when you run the presentation on a different computer. (However, note that the wizard cannot include TrueType fonts that have built-in copyright restrictions.)
If you make changes to your presentation after you package it, just run the Pack and Go Wizard again to repackage it.