****!!! I just spent 10 minutes of my life typing this out and when I clicked submit it lost it all!!! ****!!!!!!!!! Right, now I have that off my chest. Let's start again: Think calm thoughts. I just installed another 2x1GB of RAM to my system, exactly the same spec as before. The BIOS displays this as about 3.9GB but then procedes to boot normally, which is fine. The RAM is set to 1.8v (default is 1.9v). Vista gets all the way the end of the loading screen and then I get a BSOD with the nvlddmkm.dll named as the source of the problem. My computer then reboots. I took a stick out, leaving 3GB, and my computer works fine. It's possibly even slightly more responsive under heavy load due to the extra RAM. However, my Vista Performance Information tool shows a decrease in my memory speed rating from 5.4 to 4.8. My questions to you all then, are: 1) What on earth is the right voltage for my RAM? (Non-ECC) The maximum value in the BIOS is 2.3v but that is in red text which scares me a little. 2) Can I get my memory speed rating back up to 5.4? I assume this has something to do with 1 stick not being dual channel? 3) How can I get Vista to boot with 4GB of RAM? I installed a patch (KB929777) from the MS website and also the latest NVIDIA drivers but this hasn't worked. Thanks in advance guys, anyone clever and kind enough to help will get a hearty dose of reps!!