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) - Walmart.com
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
Upgrading the CPU in ThinkPad X61 — Wenting's Web Page
Upgrading my ThinkPad X61 - YouTube
4GB 2X2GB RAM Memory for Lenovo ThinkPad X Series X61 (76734NU) Black Diamond Memory Module DDR2 SO-DIMM 200pin PC2-4200 533MHz Upgrade System Specific Memory - Newegg.com