Turn a $34 Thinkpad Into a Snappy Modern Laptop: Lenovo Thinkpad T400 Upgrade Guide - YouTube
8GB Kit (4GBx2) Upgrade for a Lenovo ThinkPad T400 Series System (DDR3 PC3-12800, Non-ECC, ) at Amazon.com
OFFTEK 4GB Replacement Memory RAM Upgrade for IBM-Lenovo ThinkPad T400 (6475-xxx) (DDR3-8500) Laptop Memory at Amazon.com
4GB Team High Performance Memory RAM Upgrade Single Stick For Lenovo ThinkPad T400 Series T410 Series Laptop. The Memory Kit comes with Life Time Warranty. at Amazon.com
4GB RAM Memory Upgrade for Lenovo ThinkPad T400 (DDR3-1333MHz 204-pin SODIMM) at Amazon.com