2003 files *are* in 97/2000 format. You don't need to do anything special
when you save. PPT 97 and 2000 can open PPT 2003 files just fine.
If you do "backsave," your option is "PPT 97-2003 AND 95." That "and 95"
part will get you. Your files will become HUGE, and unless there's a person
using PPT 95 who needs it, it's unnecessary.