I used to use this on my XP machine but since I don't use XP anymore I don't need these two sticks.Technical SpecificationsManufacturer KingstonManufacturer Part # KVR533D2K2/2GRMemory Type DDR2 SDRAMCapacity 2GB (2 X 1GB)Pins 240 PinBus Type PC-4200Error Correction Non-ECCCycle Time 7.5nsCas CL4Data Transfer Rate 533MhzMemory Clock 133MhzVoltage 1.8