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I have trouble with activate 4GB memory on a Windows XP SP2 32 bit machine.
Normally Windows show's about 3.5 GB RAM when you install 4GB, but now it only show's  2GB.
The BIOS is counting 4GB memory so i think it's installed proparly. And all of the 4 memory are of the same type. How can i solve this so i at least can use 3.5 GB?
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That is because windows 32-bit doesnt support over 2GB, so you MUST switch to Windows XP 64-bit or Windows Vista 64-bit

Windows xp 32-bit will show you around 2.2GB - 3.2GB, but still it isnt supported.
XP 32 bit doesn't support over 3GB correction. you need 64 bit windows for proper operation.
It should give you close or such amount of memory, however, I would utilize PAE memory, the /PAE switch must be added to the corresponding entry in the Boot.ini file. If a problem should arise, Safe Mode may be used, which causes the system to boot using the normal kernel (support for only 4 GB of RAM) even if the /PAE switch is part of the Boot.ini file.

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Have you changed something? New Hardware? Changed somehting in the BIOS? Updated the BIOS?

I assume you have all the relevant switches in the boot.ini file?
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Nope I haven't cheked the boot.ini. Punky: I think you are into something. I found this arcticle but I'm not sure what to add in the boot.ini file. Can you help me?
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Gary Case
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garycase: i know, everybody seems too have a strong meening about this thread :0)
I will come back too you on monday when I'm back at work again. I will check what type of memory that are installed and the make of the motherbord.  Till then have a nice weekend!

When you're back at work again on Monday, take a look at these previous threads covering XP Memory upgrades from 1GB up to 4GB.  Not all comments of course are applicable, but it's worth scrolling through them all because there are several good descriptions.  Once again garycase explains the situation very clearly!

"Memory upgrade":

"Max memory":

Have a good week!
Thanks Gary, YOU ARE RIGHT and i was going to say the same thing!!!!!!! I have xp 32 bits with 3,5 GB of RAM. I was shocked when i read the first 2 responses.

Elit2007, this can be due to the graphics card if integrated within themotherboard. It will grab as much memory as it can!!

Hope this helps,
Please let me know if you have any other troubles

1)  What is the motherboard make/model?
Asus P5B13L
(2)  Run CPU-Z (no installation needed) and select each of the modules one-at-a-time on the SPD tab and see what is reported.   [ ]   Also note what is shown on the Memory tab.

Each module are showing the same information, except Part Number and Serial number are missing in slot 2 and 4.
The Memory tab shows 4096 Mbytes in the Size box.

(3)  If you only install 2 modules does the system "see" 2GB okay?
(4)  Are all of the modules double-sided (chips on both sides) ?    If so, this may be a bus loading issue ... and may be resolvable by increasing the voltage and/or setting less aggressive timing parameters.

The modules are double-sided.
With 4 double-sided modules there's a very high electrical load on the data and address bus drivers.   This can often cause issues ... which can sometimes be resolved by (a)  increasing the voltage to the memory modules [in the BIOS] and/or (b) using slightly slower memory timing.

I'd check the current voltage, and bump it up by .2 or .3 volts.   For example, if it's currently 1.8v, try 2.0 or 2.1 volts.    If that doesn't help, then I'd leave the voltage slightly higher, and relax the memory timing.   You didn't show the memory timing data from the SPD (as I'd asked you to do), so I don't know what it is now; but basically just add 1 clock cycle to each of the timing parameters.
Thank's for all help and suggestions for my problem. Since this was a customers computer i didn't got time to use a week figure this out ;0) The most I manage to get was 2,75GB with 3 modules installed.
So i took the simple way. Installed 64 bit Windows, and volla ... 4GB available memory :0)
And now the customer got the opportunity to install even more in the future :0)
It's not clear that "giving up" and reloading the system is a solution => I'd put this in the category of "didn't like the answer" and/or didn't have time to actually solve the problem ... that doesn't mean the responses wouldn't have fixed it.   I think I rather clearly detailed the issues and provided a path to resolution.
I would agree with garycase!  He has provided much information and surely in sufficient detail to qualify for a "Good Answer".    In this thread he sensibly highlighted a number of "inaccuracies", and was referred to for his clear explanation of a similar topic, in another thread.
Sorry, from the instruction's for closing a thread I supposed I had to accept my own solution when I haven't directly used other's solution. I learn something every day ;0)
Garycase: I check with the supplier of the computer. They said that if there was a problem with the  eletrical load on the double sided modules, this would result problems in the boot self test also.
And since the modules work's in 64 bit Windows this should't be the problem?
Electrical loading won't impact the BIOS test, as it runs at very conservative memory parameters --> the BIOS will, however, often slow down the memory if it detects 4 installed modules.   The Asus documentation specifically notes that it will work at slower speeds with 4 modules installed [It notes that DDR800 modules will be operated at DDR-667 or DDR-533 as needed].   It absolutely CAN cause other issues ... it just depends on the specific modules.   You can often overcome these by doing as I noted ... increasing the voltage, etc.   With an x64 OS, the potential reliability issues are still there ... but the addressing issues aren't, since the reserved address space elements can be placed much higher in the address space (out of the way of your installed memory).

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