That depends on the PowerPoint version you are using. In all versions you
can choose more than one picture at the time to import them to ONE slide, if
you hold the Ctrl-key when choosing the pictures.
In PowerPoint 2002 (and 2003 of course) you can choose "Insert | Picture |
New photoalbum" to insert many pictures in a new slide show. For PPT 2000
you can download this as a Photoalbum Add-In from Microsoft's site.