Yes and no. Most features of PowerPoint should work fine, but there are
plenty of new features that do not translate. Also, you either have to
save it in PowerPoint 97-2003 format, or the person using 2004 has to
have the compatibility pack installed.
If you have a compatibility pack installed on the mac it should. To be on the
safe side you should probably save it in a previous format. "Save As >
PowerPoint 97-2003 Format"