Autotext is saved in templates, normal.dot by default. But you do not want
to copy your old normal.dot to a new installation. First, find your
normal.dot file in Word 2000. Make a copy of it naming the copy something
like normal2000.dot. Then do your upgrade. It may incorporate your AutoText
automatically. If so, you are fine, if not, you could put your
normal2000.dot file in your Word Startup folder (Tools > Options > File
Locations). You would then have your old AutoText available (as well as
macros and any custom toolbars).
Note that AutoCorrect entries are different from AutoText entries and stored
elsewhere. See
http://addbalance.com/word/movetotemplate.htm for
step-by-step instructions on moving / sharing / copying / backing-up
customizations including AutoText, AutoCorrect, keyboard assignments,
toolbars, macros, etc.