Newbie networking question

[Chris de Pujo <fdepujo_(_at_)_nc_(_dot_)_rr_(_dot_)_com>]

You'll have to excuse my ignorance about this, but....
I have two computers attached to a hub, 1 OpenBSD and 1 WinXP, there's
a 10mb NIC on the bsd box and a 10/100mb NIC on the XP box. Windows
reports that it's card is set to 10mb. I transfer a file to the bsd box
and it transfers at a rate of 500KB/s. Now, shouldn't I be able to get
(theoretically) 1.25MB/s? I'm getting less than half, so is the 1.25
MB a sum in both directions? and while I'm asking questions what are
duplex and half-duplex (again, I should know this, but...)?
Thanks a lot.