network bridge is only 10.0 Mbps

I have 3 computers. one has 2 network cards (lets call it computer 1) and the other 2 computers are plugged into it via crossover cables in order to share the internet connection.

computer 1 is running winXP pro and so when the other two computers are on i get the little icon in the bottom right showing that the network connection is active and it tells me it is operating at 100.0 Mbps. It is the same for both computer 2 and 3.

in order to get computers 2 and 3 to talk the two connections are bridged but the bridge says it is operating at 10.0Mbps rather than 100.0Mbps. as all of the network cards are 100Mbps should the bridge not operate at 100Mbps too?

since both connections appear to operate at 100Mbps would i be right in assuming that computer 1 communicates at 100Mbps with comp2 and comp3, but comp2 can only communicate at 10Mbps with comp3 because of the bridge?

thanks