2GB Memory RAM Upgrade for the Lenovo Thinkpad R61 Series, T60 Series, T61 Series, X60 Series and X61 Series Laptops (DDR2-667, PC2-5300, SODIMM) at Amazon.com
8GB (2X4GB) Memory PC2-5300 667Mhz DDR2 SODIMM RAM for Lenovo ThinkPad R61 at Amazon.com
How to upgrade RAM memory in Lenovo ThinkPad R61 laptop - YouTube
IBM Thinkpad T61 RAM Replacement - iFixit Repair Guide