I can print from Word, but not from Windows Explorer or Outlook
Express.  What's more, in these last two programs, if I click on File
and then Print, nothing happens.  Normally, one gets a window allowing
one to specify various parameters, such as the range of pages to be
printed, choice of printer, etc. (and this in fact occurs when I print
from Word).  In Windows Explorer, clicking on Print, Print Preview,
brings up a window with a menu bar but no other contents.

I have a Toshiba Satellite L25-S121, running XP professional with
Office 2003, and a USB-connected Brother MFC-584CN printer.  The
printer is selected as the default one. This problem arose recently,
presumably because of something that I did.

Any clues, any one?

If the dialog box doesnt come up, 90& of the time it means its a driver problem.

I couldnt find your printer on brother.com (584CN)
The only one i could find that was closest was 5840CN

Link for that: http://welcome.solutions.brother.com/bsc/public/us/us/en/dlf/download_top.html?reg=us&c=us&lang=en&prod=mfc5840cn_all

Its odd that its coming up for word and nothing else. Im still going
buy my driver problem though.
Install the latest drivers from the brother website, if that doesnt
work. Rollback to the previous drivers in Device Manager.

Also check the spooling manager as soon as you go to File --> Print.

It sounds like you have file corruption issues. If you have recently
installed something, check for updates. Make sure Windows XP has the
most recent updates. You should also check for Office updates at
http://office.microsoft.com/en-au/officeupdate/default.aspx. If this
doesn't solve your problem, try rolling back to a point before you
started having issues. From the Start Menu go to Programs ->
Accessories -> Sytem Restore. Use the wizard to select a roll back
point. If none of this works, a system file might have been corrupted
in the operating system. Use your Installation disk and try to repair
your installation. Unfortunately, file corruption issues are not
reparable. This might require a complete reinstall, but only do this
as a last resort.