Correction: The last paragraph is not accurate. I made some inquiries with
the virtualization team at MS and I would have seen something closer to but
still under 4GB if VPC supported allocating a full 4GB.

"Colin Barnhorst" <c.barnhorst@comcast.net> wrote in message
news:D82153D5-F2BD-42F7-9817-74FA4D5ED226@microsoft.com...
> It's a very big tilde. My XP systems showed anything from 2.2GB to 3.5GB
> before all our computers were promoted to Vista.
>
> I use VPC extensively so I just tried an experiment to see how close I
> could get to using all the memory in a computer in Windows itself. In VPC
> I tried maximizing the memory allocation for an XP Pro vm in its vm
> Settings. I got as high as 3.62GB to show on system properties with an
> allocation of 3.712GB memory, which is the max VPC allows for a guest, on
> my Vista Ultimate x64 host. 3.712GB happens to be the max permitted by
> VPC on any host.
>
> VPC emulates very old hardware so the reservation of relatively little
> memory by the guest's BIOS makes a lot of sense. My point is that the
> hardware on a computer has everything to do with how much memory is
> available to user programs when 4GB of ram is installed.
>
> btw, if VPC had allowed me to allocate a full 4GB for the guest I would
> still have only gotten 3.62GB to show on system properties. It is the
> addresses that are being reserved.
>
> "Doug" <Doug <dougti@discussions.microsoft.com> wrote in message
> news:OamK8kvxIHA.2384@TK2MSFTNGP02.phx.gbl...
>>> BIOS and System|Properties show correct size of installed RAM while
>>> System Tools|System Information and Task Manager|Performance show the
>>> maximum usable part of the installed RAM. The maximum usable part could
>>> be as low as 2GB. Therefor,if 4GB is installed and Task
>>> Manager|Performance indicates that the Total Physical Memory is 2GB,
>>> then half of the installed RAM is waisted.
>> Correct. Your BIOS should tell you how much is detected, your OS how much
>> is available. (In simple terms)
>>
>>>> 1. PAE doesn't help on Windows client operating systems, just on
>>>> servers.
>> Fair enough. I just did a quick google to check Windows compatibility
>> with PAE. I use Unix.
>>
>>>> 2. The maximum accessible amount is not precisely 3.2GB
>> Forgive my absence of a tilde (~)...
>