Memory Limitation?

I have recently purchased a HP server that is running on SBS 2003. Actually, this server is installed with 4gb ram, but SBS 2003 is only showing 3.5gb memory in the computer properties. I have used HP diagnostic tool to check the 4gb Memory that is working properly. But why the SBS 2003 is only showing 3.5gb, is this a SBS 2003 limitation? Thanks for any information.

Remember that in the absence of the /PAE switch, the Windows memory manager is limited to a 4GB physical address space. Most of that address space is filled with RAM, but not all of it. For more information go to this website - http://blogs.msdn.com/b/oldnewthing/...14/699521.aspx

Thanks for the replies. I think that there are many people who are having the same issue. Would I be able to add another 4gb memory to this server, since I dont know how much memory SBS 2003 premium will pick up if I add a total of 8gb ram. Actually, there is this memory shortage in the server?

Actually, Windows 2003 Standard, will only support a maximum of 4gb of installed Ram. And what makes you say that there is a memory shortage? I think that 3.5gb of available Ram shall be more than enough for SBS 2003 and most line of Business applications that may be installed on it. Since SBS is limited to 4gb ram, there is no sense adding extra ram.