Right, but what I was saying was that out of that 4gig of address space you rarely end up with more than 3gigs of available system memory (RAM). Clearly my explanation was lacking, but the essence is true - installing 4gigs of RAM will not give you 4gigs of usable RAM. Based on the way the OP phrased the question I figured implementing the KISS principle was probably best. All that said, you're 100% right in your explanation from what I can tell.