Alternatively, you could try going into your wireless config pages (either in your third party manager app like Intel provide for their chipsets) or the Windows manager, go into the advanced properties for the connection, go to the dialog where it shows the asterisked encryption key, and use one of these tools:
http://www.nirsoft.net/utils/astlog.html
http://www.soft-central.net/passunleash.php
or similar (there's quite a few about, google "show passwords windows xp" or "reveal passwords windows" for more results), and that *should* work.
Very useful if you have an AutoSaved login and you forgot the password - happens a lot to me because I'm a bit scatterbrained!