I have a HP Pavillion ZE2117US. I bought a 1GB ram stick. From all my research to the best of my knowlege its the right one. I pulled out the 2 256MB sticks and installed the 1 gb. I started the computer and got the HP splash screen and windows started. I logged into windows and then got a BSOD. I don't know what the error was as it restarted to fast. If I put the old sticks in everything works fine.