text changing when opening an AutoCad 2000 drawing with AutoCad 2004

Answer 1

If the font doesn't exist in 2004 it will revert to a default font and perminantly replace it.  Sometimes a dialog box comes up and asks if you want to replace it - sometimes it doesn't.  In the properties, there's a files tab that should tell you where each program stores their fonts.  Use windows to copy the fonts from 2000 into 2004 and that should fix your problem. 

As far as the drawings that have already been changed, you might need to globally change the fonts back.