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8GB (4GBx2) Team High Performance Memory RAM Upgrade For Lenovo ThinkPad T400 Series T410 Series Laptop. The Memory Kit comes with Life Time Warranty. at Amazon.com
4GB Memory for Lenovo ThinkPad T400 7417, 7420, 7425, 7434-xxx DDR3 PC3-10600 1333MHz SODIMM RAM (PARTS-QUICK Brand) at Amazon.com
HD] Installing RAM on a Lenovo Thinkpad T420 Guide T410 T400 - YouTube
Lenovo T400: How to upgrade the RAM - YouTube
4GB DDR3 Memory RAM for Lenovo ThinkPad T400 2764 at Amazon.com