I recently installed Windows 2008 Server Standard x86 on a HP xw6000 Dual Xeon workstation. The install went fine, the OS runs fine, however there is 4GB of memory installed and Windows is only showing 2.62.
When I look in the BIOS it shows 4gb...when I run SiSoft Sandra it shows 4GB (4x1GB modules)
I ran the memory test from Memtest.org, stopped it to do other tests, but am going to let it run again over night. When the test was running, it showed only about 3.2 or 3.6GB of memory (somewhere in that range)
I figured for a second that it might be a BIOS limitation that would not communicate properly with Windows, however even SiSoft said that the max memory for the board was 8GB. I updated the BIOS to the most recent version, which is still a few years old.
Lastly, I ran systeminfo from the cmd prompt and it shows the total physical memory being 2,687 MB.