Hey guys, I had a problem with this memory stick im trying to install, I thought I would get some insight on what the problem could be. I have a 1.9Ghz iMac G5, I bought it right before the Intel ones came out. I was given an unopened 512MB PC4200 533 DDR2 stick from a friend of mine who wasnt using it since he upgraded to a 1gb and was given this unopened stick of ram with his order for reasons unknown, so I ended up with it for free. Cant beat that. I installed the memory through the memory slot at the bottom as manual shows, machine turned on fine, but never recognized the memory as being there. DIMM1 slot kept telling me Empty. I tried this 3 or 4 different times thinking that I installed it wrong. Searching around, it is very hard to find specific information on what ram is compatible with this machine, or maybe I'm just looking in the wrong place? Here are the exact specifications on the stick itself: 512MB 1RX8 PC2-4200U-444-12-D0 512MB, DDR2, 533, CL4 Maybe this is for the intel Imacs? I'm fairly new (2 months) to using a mac and havent used it long enough to know enough about the hardware aspects of it. Does anyone have any insight on what the problem might be, or if this stick is not compatible with this mac? Thanks in advance for any help.