Windows 7 uses only 3.99GB memory

I have a new Dell XPS computer with Intel i7 processor, Windows Home Premium 64 Bit installed.  It has 8 GB memory installed but says only 3.99 GB is usable.  I have tested the memory, ran all the motherboard diagnostics, and the latest BIOS is installed. Does anyone have a solution other than replacing the motherboard?
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Are you sure it's a 64bit install???

Right click on My Computer and choose Properties.  Look at the System Type to make sure.
carstAuthor Commented:
Have done so!  Still shows only 3.99 usable.
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apparently you have to enale 'Memory Remapping' in the BIOS
carstAuthor Commented:
That is not available.
how you fixed ram on motherboard ?

1DIMM has 4GB
2DIMM has 4GB

is this what you did ? how many slots you have? try shifting ram among them..

do you see 8GB ram in BIOS?
Are you sure you're interpreting that correctly?  I have 4gb ram installed, no page file and perfmon shows 2.5 gb available indicating that I have that much of my 4gb that is currently unused.  It is still there and available when needed.  That's why I turned of my page file since I have enough extra RAM to work without the slow disk acess' for paging.  my ram gadget thingy shows 38% used so that would leave 62% avail or c. 2.5 gb.  If the PC is working ok then you probably don't have a problem just not understanding what it's telling you although the number seems a little low in your case.  
carstAuthor Commented:
Dell support has agreed that the motherboard is at fault and is replacing it under contract.  Will post the results later today.

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Abhay PujariCommented:
ok. Good to hear updates.
carstAuthor Commented:
Dell Replaced motherboard and power supply which fixed the problem.  No points awarded.
Thanks for the update and glad that worked!
if yours question is solved pls close this question
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