Ok, follow this closely:
Go here:
http://www.linksysbycisco.com/US/en/support/BEFW11S4Click on "Get Downloads", on the drop down menu, select
version 4.
DO NOT SELECT ANY OTHER VERSION
On the left under "Downloads and Drivers", click on the "download" link and save the firmware file to your windows desktop..
Next, open a browser and type the IP address of your router and press enter.. On the main page, click on "Administration". Click on the Firmware Upgrade tab, click on the Browse button to select the Firmware File that you downloaded to the desktop... Click the upgrade button. After it finishes, go to one of your older laptops and connect to the Internet to confirm that the upgrade was successful. (you might have to configure the router's WiFi password again or other setttings..)
If you can connect using one of the old laptops, try connecting with your wireless-n laptop to see if the download speed has improved.. If not, unplug the router and turn off your wireless-n computer.. Leave your router off for a few minutes and power it back on... After all the lights have come back on, power the wireless-n computer back on and try connecting/testing the speed...