1GB RAM Memory Upgrade for the HP Pavilion d4650y, a6400f and a6257c Desktop Computers (DDR2-667, PC2-5300) Guaranteed Compatible for the HP Pavilion d4650y, a6400f and a6257c Desktop Computers Speed up your system with up to 4.0GB of Memory! Lifetime Replacement Warranty! Will ship the same day when ordered at or before 4pm EST! All others ship next day! Fully-staffed call center to help with installation or inquiries! Call 866-335-1355 with questions or for help!