I have just been building up a PC from older spares for a mate of mine, she had a shite slow p3 celeron 1.x ghz thing, so i made up a p4 2.53 for her, which is much better, still not modern, but at least it doesnt freeze and die all the time, but the only RAM i had to hand was 1x256 and 1x512 stick, totalling 768, which i fitted and it worked ok, but then i remembered that the old one also had 768mb fitted, and this p4 i built has 3 mem slots, i removed it from the old machine and fitted it into the newly built one, so it now has 2x512 sticks and 1x256 stick, totalling 1280mb, and i arranged it like so, starting nearest the CPU, 512-512-256 which im sure is correct, biggest chip nearest the processor, smaller one in the end slot, but windows is only seeing 768mb still if i look in control panel > system, yet it does seem quicker, plus if i run PC wizard it shows that all 3 banks are filled, and what size sticks they are, but the 2nd one, one of the 512's although it shows module size etc, shows serial number and make as unspecified, so pc wizard can see it, but cant identify it.

So my main question is, eventhough windows doesnt appear to show it, pcw does, so is it actually in use, because as i say, it feels better than it did, but im not sure if its actually making any difference in there.

i'm thinking two things...

the bios might have a maximum memory limit, but since it's a p4, that's probably not likely.

the other thing, is that the sticks might not be compatible with each other. when you acquire random sticks of ram, it's bound to happen... i've had it happen to me a few times. eg: stuff 128mb into a system, and then add a pair of 64's, and when it boots up, it shows 96mb. how it would end up with less than what it started with is a brain****.

in short, windows will not use memory that it didn't pick up. other programs might see it but if windows doesn't see it, there's a fair chance it's not being used.

Why not put all 3 512's in? Also, are they the same speed?