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Why does Windows only show about 3.5GB of my 4GB+ of RAM?

I have recently purchased 8GB of RAM to upgrade my system to go along with a new shiney i5!

When I run speed checks on my system it online I get told I only have 3.5GB of RAM, also in the task manager I only see around that value of RAM yet that stupid Windows rating Index tells me I have 8.0GB

Any Ideas what I am doing/reading/interpreting incorrectly?!?!

See below what I see:

Information about my system

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migrated from stackoverflow.com Oct 21 '11 at 16:55

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marked as duplicate by shf301, Shinrai, Nifle, Kyle, DragonLord Oct 21 '11 at 17:26

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One would think that this is common knowledge by now. –  Daniel Beck Oct 21 '11 at 16:57
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4 Answers

You have a 32 bit operating system. Because of this, your computer can only address 4GB of the available RAM. That means, no matter how much you can stuff into your board ( or how much your board can handle ( as that could also be an issue )) your OS will only ever be able to work with 4GB of it. The only real fix is to upgrade to a 64bit operating system.

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4  
And it's less than 4GB because of memory addresses for other hardware, primarily graphics card. –  Daniel Beck Oct 21 '11 at 16:58
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The clue is in the screenshot you provided, you're running a 32 bit OS which will only support 4GB of RAM:

enter image description here

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You have a 32-bit version of Windows, which can only use 4GB maximum because 2^32 is 4294967296. Some of that 4GB is used for other purposes, so 3.5GB is about the best you can do without a 64-bit OS.

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According to Microsoft, 32-bit versions of Windows 7 (which you are using) are limited to 4GB of physical memory.

Memory limitations

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