I booted up my Windows rig today to play Left 4 Dead, and found that it decided to only read 2GB of ram.

Did a quick CPU Z on it and 2 sticks (out of my 4 x 1GB) are reporting serial numbers of FFFFFF etc, switching slots shows the same two sticks displaying as 'faulty' each time. Which I could believe if it weren't 2 sticks and they hadn't both 'failed' at the same time. However CPU Z does read 4096MB total.

BIOS shows 4096MB fine, and 64bit Linux shows 4GB fine. I tried looking at my boot.ini to see if it was restricting the memory usage at all, the max value I could set in MAXMEM was 2048MB

I am aware of the limitations of 32bit Windows, it previously read around 3.5GB or whatever the limit is, which wasn't really a problem. So it's not the problem of it being 32bit here.

This Windows installation is getting pretty shot with junk now anyway, time for a reformat do you think? Or any other suggestions?

Not realy a great help:
http://support.microsoft.com/kb/555223/en-us

Hmm thanks anyway.

Here's something new, it's exactly the same after a reformat :/

http://support.microsoft.com/kb/291988

Better off with a 64-bit native OS than a hack, imo.

Think you're probably right tbh. PAE was on by default this time around (:/) think I must have turned it off before. Tried the 3GB param to no avail, and maxmem=4096 etc, again no luck.

Running Memtest86 now to see if it really is the RAM, no errors yet 10 mins in.

So my next question, how is XP 64bit these days? Drivers seem pretty much all available. I'm not going for Vista as this is a highly streamlined installation of Windows used purely for games and I could do without Vista's useless background services.

Have you tried removing the RAM from the sockets, cleaning the sockets, and switching the modules around? The solution can be a lot simpler than you may think.

As for XP64, I tried it not too long ago but it just seemed slower that XP32, which I found to be very odd. Also I got pissed when I couldn't install Java 64-bit edition, when IE7 64-bit edition didn't work, and when it took more than 5 seconds to do a simple operation, so that's when I ditched it. XP32 runs much faster on the machine in question for no reason whatsoever. Just my experience.

For 64bit, Vista is the way. It just is. It's a breeze to disable all the pointless (for a gaming rig) services through the services control panel, and then you're basically left with XP with DX10 and Aero, which you can also disable. Don't see the problem to be honest.

The /3GB switch can get you a long way, but for some reason Microsnob decided to limit the registry file size when using it - meaning that you wont be able to have as much software installled.

I've run into this limit (without having junk on my computer - but I do use my PC for many things and have therefor many apps installed), but IMO it would be fine for most users.

Cheers for the replies guys.

I did try swapping the sticks over but no luck.

I think perhaps I'll get Vista 64bit at some point in the future, think I've got a legit copy of Business knocking around here somewhere.

I did try the 3GB switch too but I think there's something a bit more weird going on, as that didn't help.

Still, it's not a big issue as 2GB is fine for gaming atm, and as there's hardly anything else running it never gets close to running low.

I think one or two of your sticks are broken, because there's no reason why all of sudden Windows wouldn't recognize them. Is it possible to try some other sticks of ram from another computer?

Did you by any chance turn the memory hole remapping feature in the motherboard off. Same thing happened to me when I was using 32bit Vista ult. but bought vista ult. 64 bit and turned it on and voila all the 4gb shows. on a side note though the hole remapping thing only allows 3.25 gb of allocated memory in 32bit(insert microshit windoez version here).

Quote from shiny_red_cobra :

I think one or two of your sticks are broken, because there's no reason why all of sudden Windows wouldn't recognize them. Is it possible to try some other sticks of ram from another computer?

Nah they pass Memtest86+ with no problems, and display fine in 64bit Linux. No spare RAM to try though sadly.

It used to read as 3.25GB or whatever was left from the 4GB limit, but suddenly stopped the other day.

Out of curiosity, what if you take out 1 GB, and leave 3 GB in, what does Windows show then?

Did you recently install any GFX Cards with high amounts of memory?