4GB 2 X 2GB PC2-5300F 667MHz 240 pin DDR2 SDRAM ECC Fully Buffered FB DIMM Server Low Power Memory for HP Workstation XW8600 (PARTS-QUICK BRAND). Equivalent to HP Part Numbers: 397413-B21, 442823-B21,
URAM 2GB DDR2 SDRAM 667MHz PC2-5300S SODIMM Micron IC RAM Module (Computer Laptop Memory) at Amazon.com