I have a working debian web server with a 1gigabit network connection.
It is serving this speed fine to any linux box, i.e. a web browser in a linux enviornment downloads at 1000Mbits/sec, but when I try this from any windows box it maxes out at 10.4MBytes per sec i.e. approx 100Mbits/sec.
I have tested 2 identical windows xp boxes via cross-over and they transfer at 1gigabit with no issues(although I did not test via a web browser, just file sharing).
I removed both the debian server and windows box from the network and used a crossover cable between them, but still stuck at 100Mbits/s. I am using the latest network drivers avaialble for the windows xp box.
But here is the reason why I think it might be web browser related:
I subsequently installed a samba server to the debian webserver. Then, from the windows box, I mounted a folder using "map network drive" and xp transfers from this mapped folder to its desktop at 1gigabit.