We had bought a New Microsoft Windows Server 2008 Enterprise Edition (32 bit) for Database usage. We are using Microsoft SQL 2008 Enterprise (32 bit) The physical RAM is 20 GB I wonder how could we fully utilize the RAM since the server only act as DB Server.

32 bit operating system has the limitation for 4GB no matter how much RAM you install. I advice you to go with the 64bit os Windows 2008 r2http://technetfaqs.wordpress.com

Thank for your reply. But according http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx, Windows Server 2008 should support 64GB if we had enabled PAE. Does this mean we do not need to upgrade the OS?

Hiya, You can set the min and max memory allocated property for your SQL server. That way it will load as much as possible into memory and let it stay there until its filled up and something else needs requests memory. (which is not loaded) Altho I belive its standard SQL behavior to start "eating" memory, its still a way to control it.Make sure that you with maximum setting leave enough for OS to operate. 4GB should suffice.

Enabling PAE, will limit to the OS to 2GB total. What PAE does is dedicate 2GB to OS and the other 2GB to anything other then the OS.http://technetfaqs.wordpress.com