AutoTexts still exist in Word 2007, as a gallery, or "subset," of building
blocks. Other examples of galleries are Header, Footer, Page Numbers, Table
of Contents, Watermarks, and Quick Parts.

The advantage of the various galleries is that they determine where you
should see a particular item and how it should be inserted. For example, a
building block entry in the Header category can easily be inserted into
headers, for example, via Insert tab | Header.

You can look at Insert tab | Quick Parts | Building Blocks Organizer to see
the available building block entries, and for each bulding block you can see
which gallery it belongs to as well as other information (for example where
it is saved).

To create an AutoText entry (or any other kind of building block), you can
do the following: Create an example item, select it, and press Alt+F3, as in
previous versions. Choose the desired gallery and other options for your
building block.

AutoComplete is no longer supported in Word 2007, but you can type the name
of a building block and then press F3 to insert it.

Alternatively, use a formatted AutoCorrect entry instead; AutoCorrect
remains unchanged in Word 2007.

For more on building blocks, see also this article:

Create and use content Building Blocks in Word 2007 documents
http://office.microsoft.com/en-us/word/HA102341311033.aspx?pid=CH100626151033