You won't see 100 mpbs if you're using a hub...you'd only see that with a switch.
I'm not totally sure on this, but from what I understand this is how hubs and switches work:
A hub essentially "splits the bandwidth" between ports.
If you have 5 ports on a 100 mbps hub, each port will be alotted 20 mbps.
100/#ports = most bandwidth each port will get.
A switch has the added technology of giving more bandwidth to ports that are in use. So if only two ports are connected and one is sending and the other receiving, each one will get 100 mbps.
I may be wrong on some of this, but I think thats generally how things work.
As for your 900k/s cap when you should be getting 2000k/s, drivers and settings are where the problem would be. Make sure you set the NIC to run at 100mbit full duplex.