Well I tried 64bit and although it showed the full 4gb and used it, it wasnt very stable (dont know why) So I have gone back to Vista 32bit and will wait patiently for W7.
EDIT**
Just found this on the incredibly slow ASUS site.
http://support.asus.com/faq/faq.aspx...Language=en-us
Quote:
If you installed total 4GB memory, the system will detect less than 4GB of total memory because of address space allocation for other critical functions, such as:
- System BIOS (including motherboard, add-on cards, etc..)
- Motherboards resources
- Memory mapped I/O
- configuration for AGP/PCI-Ex/PCI
- Other memory allocations for PCI devices
Different onboard devices and different add-on cards (devices) will result of different total memory size.
e.g. more PCI cards installed will require more memory resources, resulting of less memory free for other uses.
On a SLI system, since PCI-Ex graphic cards will occupy around 256MB, another 256MB will be occupied after you install a 2nd PCI-Ex graphic card. Hence, 2.75GB memory left only if two SLI cards installed on A8N-SLI Premium while 3.0GB memory left with one graphic card without other add-on devices.
This limitation applies to most chipsets & Microsoft Windows 32-bit version operating systems.
If you install Windows 32-bit version operating system, we recommend that you install less than 3GB of total memory. If more than 3GB memory is required for your system, then below two conditions must be met:
1. The memory controller which supports memory swap functionality is used. Chipsets later than Intel 975X, 955X, Nvidia NF4 SLI Intel Edition, Nvidia NF4 SLI X16, and AMD K8 CPU architecture support memory swap function.
2. Windows 64-bit OS which can address more than 4GB memory.
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So it seems that my 2 & a half year chipset is by and large underspec to see the correct amount of memory when the BIOS is remapped or not.