need to redirect .php?t=x to another dir

[COBRAws]

sup guys.
(i think this is the right section, if not, im sorry)

I recently changed my forums dir to another one, and of course, im gettin a huge 404 error log file (i knew this would happend, so i dont bother).

What i would like to do is redirect visits sent to the old forum dir to the new one.

example:

if a user goes to mysite.com/forum/forumdisplay.php?f=1
it redirects to mysite.com/board/forumdisplay.php?f=1

thank you very much.