The sources specific to a document are stored inside the document. So you
can work with those at all times.
Your master list (all the sources you ever generated) is stored on a single
computer. However, you can easily copy your master list between computers if
you wish to use the same master list on multiple computers. The default
master list is stored in "sources.xml" which is located under
"%appdata%\microsoft\Bibliography\" If you don't find it there, in Word
2007, you can go to the "References" tab and click on "Manage Sources".
There click on "Browse...". The default directory where it opens in is the
directory where you stored your master list.
An alternative way of transporting the master source list is through a Word
2007 document. Open a new document. Go to "References", "Manage Sources".
Select all sources from the master list (left list) and use the "Copy ->"
button to copy them to the current list (right). Quit the source manager and
save the document. Then on your fresh install, open the document, go to
"Reference", "Manage Sources". Select all sources in the current list
(right) and use the "<- Copy" button to copy them to the master list (left).
Note that you can store your masterlist in a more convenient place (together
with your documents) and then use the "Browse..." button under "Manage
Sources" to select it.
Yves