Actually its 3GB, ask me how i know. No it's 4GB, minus address space for hardware. Could be ~3.6GB, could be below 3GB. Any hardware sitting on the system bus uses up address space in the 4GB range, from sound to video(Onboard or off) or anything else for that matter. The more expansion hardware you have installed, the more address space is reserved. 4GB is shit these days, I regard 8GB as minimum and I run 16GB in my main desktop. DDR3 is so cheap compared to everything before it, 8GB doesn't set you back much. I was running 32GB in it, until I upgraded my server and opted to steal 16GB out of it for the server rather than buy more. 32GB WAS overkill... I mean though you may install 4GBs only 3GBs will show up, it's limited by the 32bit bios.