As Lanwench said, it [top-posting] is used in Usenet (aka newsgroups) but
where bottom-posting is the de facto standard (Microsoft groups users are
used to top-posting because that is what Microsoft stuck them with as the
behavior in OE).  You already used top-posting in your reply post to
Lanwench because you put your reply at the *TOP* instead of at the bottom.

OE can now be made to bottom post using a registry hack which was described
in SP-2 for Windows XP (read Microsoft's KB article #886340) so you need to
be using Windows XP and apply SP-2.  Yeah, I know, it is the extreme rare
few that ever bother reading about what changes or fixes are provided within
a service pack.

Note that top- and bottom-posting is just one aspect regarding how to reply
to posts.  When replying, you should include some of the post to which you
are replying (because your reply may show up on a user's NNTP server before
the original post shows up) but usually you should not include all of it.
Trim off the garbage from the quoted portion in your reply.  Unless you are
replying to everything in the original post, just include enough to provide
context to anyone else reading your reply.