Sorry. I read your post three times and couldn't find the make, model, version and the BIOS version of the machine or motherboard.
Put it in bold so it stands out for me.
I recently picked up some new RAM. I started off with 1GB of Corsair PC3200 (1 stick). Initially, I bought 2 sticks of 512 MB Kingston PC3200. When I installed this with the corsair stick, my PC wouldn't boot. I checked the motherboard's manual, and it turns out that it will not boot any configuration of 3 sticks.
Fine, so I go buy another 1 GB stick of Corsair to match my first stick. Now, with all 4 sticks in, totally 3 GB, the system boots, but BIOS only recognizes 2GB. I know the Kingston works, I was using it without the Corsair while I was waiting for the second Corsair to come. Obviously, the Corsair works too. So why does the Kingston stop working alongside the Corsair?
I know its iffy to mix ram, but these sticks are exactly the same type and speed, all PC 3200. It looks to me like the chips are laid out the same way too. Does anyone have any idea what could be causing this?
I am using Vista 64-bit edition now too, so it shouldn't be an addressability issue right? Even if it was, the motherboard should still be able to recognize all 3 GB.