2 identical systems one nic running slower

Ok I have to identical systems, both have built in nics, both are running totally updated WinXP. They are networked through a Dynex DX e401 router, and that in turn is connected to Comcast cable internet.

System 1: when tested shows that it has a 100mb lan connection.

System 2: Shows the same lan connection speed.

Both systems have their settings on the nic, lan connections etc the same except for the ip addresses which they get from the router.

The problem...

System 1: shows an internet connect rate of 1024 kbps

System 2: shows only a connect rate of 768 kbps

Any idea why system 2 would be running so much slower when they are the same boxes, mb's processors etc..

P. S. I have tested cables and even swapped them and its not the cables.

 

where are you looking to see these speeds of 1024 and 768. Is it in the router config or on the pc's themselves