VM not registering the extra RAM after update

Hello all,
 I am having a problem with my VM not registering extra RAM on Server 2008 R2. After a recent update and reboot, I noticed that my RAM is incorrect. I have 16G of RAM on my machine, but it only reads 12G. I understand that the PAE needs to be enabled in order for it to show on a 32 bit OS, but I have a 64 bit OS. There is 3 virtual servers allocating 4G max on each, which is 12G, but where is the other 4G? It was registering prior to the update! Help!
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Is this a Microsoft HyperV or a VMware server?
What version?
Is the BIOS reporting the 16Gb now?
Was it originally 12Gb and you added 4Gb to it?
Carlisle_AgentAuthor Commented:
It is Microsoft Hyper-V Virtualization, Microsoft Server 2008 R2 Enterprise, and is there a way to check the bios without having to reboot the server? Reason being, we have users currently connected to the machines working on it, and I would hate to hault production in order to check this. Also, it was originally 16Gb prior to the update, but is now registering 12Gb after reboot.
what update did you do
Install Open Manage server administrator managed node, this will tell you all firmware versions and will tell you if you are having hardware issues that would reduce the total memory being seen by the OS.
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Carlisle_AgentAuthor Commented:
It was a recommended update by Microsoft updater. It was about 50+ updates since we are really unable to do this during business hours (which I should have made more time after hours for this). The Open Manage is not an option due to the incompatiblity with our HP hardware (which I have tried this before). But like I was saying under prior post, all was well untill the update/reboot; It was recognizing the 16Gb of RAM. /pulls hair out! I would really hate to revert back to a privious date, while I'm sure there is always a simple solution to the most complex of problems. =(
Carlisle_AgentAuthor Commented:
Turns out that the RAM is not registering because of a motherboard malfunction. I checked every slot with back-up RAM and found that one was burned out. I called HP and was still under warrnty, so they will replace it. Somehow, updating was not the problem?! Thank you HP for having an awesome QC fail checking procedure (/sarcasm).

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Carlisle_AgentAuthor Commented:
After a week, I have accepted my own solution. I didn't expect anyone to answer my question as promptly as they did, THANK YOU. Hardware is unlikely the solution to most IT problems, so I deemed it irrelevant in troubleshooting this brain-buster. In close, I thank those of you who responded to my question.
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Windows Server 2008

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