Vista x64 Displays Wrong Physical Memory Size

This is a crazy little problem in Windows Vista x64 that shows the wrong information when the System Information (msinfo32.exe) is run. This issue occurred on a computer that was upgraded from 4GB of DDR3 (4x1GB) ram to 8GB (4x2GB) of DDR3, running Windows Vista Ultimate x64.

What happened is the Installed Physical Memory displayed correctly at 8.00GB, but the Total Physical Memory only reported as 4.00GB and Available Physical Memory reported as 5.22GB. View the screenshot of this output below.

Incorrect Total Physical Memory

The symptoms of this problem, as detailed by Microsoft is as follows:

The Microsoft System Information (Msinfo32.exe) tool reports the incorrect amount of physical memory in a Windows Server 2008-based or Windows Vista SP1-based computer that has more than 4 gigabytes (GB) of physical memory installed. Specifically, the tool never reports more than 4 GB of total physical memory. For example, assume that a Windows Server 2008-based or Windows Vista SP1-based computer has 8 GB of physical memory. However, the Total Physical Memory item under the System Summary node in the Msinfo32.exe tool reports less than 4 GB of memory.

The cause of the problem is:

This issue occurs because an incorrect data type is used to calculate the total physical memory in the Msinfo32.exe tool.

According to the Windows Task Manager the system was using 8GB of memory, but we could never get the memory to increase beyond 4GB of usage which was strange (although not 100% confirmed) but programs like VM Server recognized the added memory, while prime95 did not.

Luckily Mcrosoft has released a hotfix for this stupid little problem.  You can get the patch here