writing form contents to a file

[Psybar Phreak]

hi again - big thanks to everyone who helped out with my last question about
reading from a file, but now i have a simlar prob, only the other way
around - WRITING to a file, only a little more complicated

i have a basic HTML page that has two form elemets (just text boxes - name
and password), and what i want to do, is write them to a file in the form
username
password

the two text boxes on the web page are label usernameField and passwordField

not quite sure where to start on this one, so any helpw ould be greatly
appreciated

thanks all!

daina