I just bought a 512MB DIMM stick of PC133 SDRAM for my Pentium III machine. It runs at 500Mhz and is not overclocked. I bought the memory along with an ATI Radeon 7500 64MB video card. Anyway, when I brought the memory home everything was going great. I opened up my PC, grounded myself and proceeded to install the video card. I hooked up the monitor, mouse and keyboard and turned it on. All was well, so I shut it off and disconnected it and installed the memory. I installed the 512MB strip beside my existing 128MB strip. When I booted it up, I checked the System Properties, and the computer reported the memory as 384MB. Okay, so I went and reversed the order the memory was in. Same thing. Then I tried putting in just the 512MB strip. Same thing, 384MB. I can't figure out why this would be happening. Any ideas?