I finally got my Win 7 Pro and did a clean install of 64bit. The first thing I checked was System Properties. I wanted to see all 4GB of ram being used. Much to my surprise, it says Installed memory (RAM): 4.00GB (3.00 GB usable) This is the same as the 32bit said. Why is it not using the entire 4GB? Rich

This behavioris due to "memory mapped IO reservations". Those reservations overlay the physical address space and mask out those physical addresses so that they cannot be used forworking memory. This is independent of the OS running on the machine. Significant chunks of address space below 4GB (the highest address accessible via 32-bit) get reserved for use by system hardware: BIOS including ACPI and legacy video support PCI bus including bridges etc. PCI Express support will reserve at least 256MB, up to 768MB depending ongraphics card installed memory What this means is a typical system may see between ~256MB and 1GB of address space below 4GB reserved for hardware use that the OS cannot access. Intel chipset specs are pretty good at explaining what address ranges gets reserved by default and in some cases call out that 1.5GB is always reserved and thus inaccessible to Windows.MCSE, MCSA, MCDST

Check for Advanced BIOS options such as "memory hole" or "memory remapping". Changing them can sometimes help free some of the memory.Your display memory will probably not be available, especially if it is onboard video. For example on my ECS A780GM-A Ultra, I have 8GB installed. I set the shared memory for the onboard video to 512MB. Windows shows 8.00 GB (7.49 GB usable).

Thanks. I'm just surprised. I always thought that moving to 64 bit Win 7 would allow me access to more of my installed ram than I had running 32 Win 7. As far as I can see, nothing has changed, though the system feels faster, but that may just be my imagination as I have no specific 64 bit apps installed except Windows Security Essentials. Ah well, at least I'm done with RC1 now. One improvement I did notice is Network browsing is faster. There is no longer a 40+ second delay when I first open Network like I had with RC1.Rich

In Windows 7 64bit all of your 4GB memory should be able to be used. The behavior in your system can be caused by the BIOS. If the issue persists after you enable the memory remapping feature, you need to upgrade the BIOS to the latest version. If it does not help, it is better to contact the motherboard manufacture and notice them the compatibility issue.Arthur Xie - MSFT

Hi RichIn addition to the other information, there is a new KB article that describes these issues and explains how to use some of the tools such as the Resource Monitor to monitor the RAM usage on the system.The system memory reported as (usable) in the System Information box in 64-bit Windows 7 may be less than the amount of installed RAMHope this helps.Thank You for using Windows 7 Ronnie Vernon MVP

That's an interesting KB article Ronnie. But it gives false hope to many readers. It doesn't sufficiently emphasize that a very significant percentage of chipsets produced up until recently are just plain limited to 32bit (4G) address space. Many of those do not provide any means to REMAP the pci-overlapped dramonto the 4G boundary either.There's a long distance between the usable 3G that Rich's system reports, and the 4G that are installed.Had his 925X chipsetsupported REMAP, much of that memory would have been usable with 64bit Windows.There's nothing the BIOS or any other configuration cando to change that fact. I don't know about old chipsets.I have an old (NVidia 4) chipset MB with 8 GB on it. In System it shows 8.00 GB. Task Manager shows 8190 MB Total Physical Memory.