netgear WNR854T router - slower DSL speed on one laptop...

I bought Netgear WNR854T gigrouter.I have 2 laptops - one has gig
port, another one has 10/100. When I connect both behind modem - no
issues, speed around 5.01Mbps
But when I connect both behind netgear which goes behind modem, the
laptop that has gig port gets same speed while laptop with 10/100 port
consistently gets a little smaller speed - like 4.9Mbps. I thought its
maybe some issue with port speed negotiation, but I dont see anywhere
to control these settings on netgear. Any ideas? I'd comprehend if its
random, but this issue is very consistent between 2 laptops!
Would appreciate any help - arkadhome@hotmail.com
Thank you
Arkadiy Shapiro