PNY Optima 4GB (2x2 GB) DDR2 800 MHz PC2-6400 Desktop DIMM Memory Module Dual Channel Kit - MD4096KD2-800 Memory capacity upgrade provides improved system performance and responsiveness Deliver all the productivity your PC has to offer with PNY Memory Compatible with PC2-6400 (800 MHz), PC2-5300 (667 MHz), and PC2-4200 (533 MHz) systems Helps prepare your PC for running Windows Vista Easy installation, Free 24-hour Technical Support, and Lifetime Warranty!