Windows not matching Virtual Center

May I know what report of VC is attached in the second screen-shot ?

The default "Memory" report

I would like to confirm whether you had monitored the RAM Usage in Windows VM over a period of time.

Yes this has been happening for 2 or 3 weeks since the creation of the VM.

The only way of comparing both of them would be to monitor the Memory Report of vCenter with perfmon built-in within Windows running both of them for a fixed time period which would ease comparison.

Can you help me get started with Perfmon on a Windows Server 2008 server?
Is Perfmon built into server 2008?

This should get you started
http://technet.microsoft.com/en-us/library/cc749249.aspx?ppud=4 

Here are the screen shots from this morning.  Windows shows the VM as perfectly quite, VC shows it using around 75% the whole time.

We get constant alerts from Virtual Center when the Memory gets this high and it's getting really irritating.
VC.JPG
PerfMonMemory.JPG

Is the VM set with any Reservations or Limits as ?

Not sure what you mean by reservations or limits.
I've set the VM to have 4Gb of memory.

Please see attached screenshot.
What is this about? I've set my VM to have 4Gb of memory on the Hardware tab, but on the Resource tab it looks like it's set to unlimited...?


Memory.JPG

Setting the VM with 4GB of memory does not limit it only to 4GB, which is why the Unlimited option is checked.
If the VM has a genuine requirement for 6GB of RAM, then the VMKernel would provide the same.

So what is my best practice here?
Should I leave it at unlimted or limit it? Will it have any effect on my problem? Is this what you were refering to with Limits and Reservations?

Limits and Reservations would be helpful when you want critical VMs to be up and running all the time and prioritize based on the requirements.
I would suggest leaving the setting to Unlimited.
Unless you have a genuine requirement and understand the pros and cons of Limits and Reservatoins, I would recommend not meddling with them.

I will leave them alone then.

Any idea on the memory usage snap shots from above?

GWitek - I am unable to address this particular concern, I apologize.