AutoCAD 2006 has a 100% WYSIWYG (What You See Is What You Get) Multiline Text "Mtext" editing. Just in case you need the older AutoCAD 2002 Mtext editor in AutoCAD 2006 for some specific reason, you can use the following:
To get the old MTEXT editor in AutoCAD 2006
MTEXTED = OLDEDITOR
MTEXTFIXED = 1
This being said the new Mtext Editor is really nice and there should be little to no need to revert back to the old Mtext editor.
To get the default new Mtext after making the above changes:
MTEXTED = "Internal"
MTEXTFIXED = 0