Generally the more the better. Though, if you want to know exactly how much just look up the system requirments for whatever server OS you plan on installing. And don't forget to take all the applications into account aswell.
Server 2003 can run on 512mbs. But if you want that server to be your domain controller, host a database, do file sharing and maybe control your DNS aswell, 512mb wont be of much use to you.
how much memory does xbox live need/
If a server object is not loaded in the memory and the request for it, then the server object is loaded in to the memory and is initialized
memory
As much as you can give it. Architecturally, Linux can support 64 GB on an x86 server, and a theoretical 16 exabytes on an x86-64 (no current server can come close to supporting that much RAM in hardware).
RAM in a server is not tied just to the number of users; it has to do with what the server is doing, which applications it is running, and their size as well. You need to run a baseline analysis of the server and possibly Performance Monitor after that to determine if the amount of memory is insufficient. Most servers do not allow users to log in directly, so more information would be necessary to completely answer the question, especially in terms of what these users would be doing, how they would connect, and if all 500 are using the server at the same time. You may have network bandwidth problems before you see any problems with server memory.
19.2MB
Infinity
27 Blocks of memory on the Nintendo Gamecube.
That depends on what operating systems you are trying to run. WIndows Server 2008, for instance, requires a minimum of 512 MB. It is best to never use more than half of the memory available on the computer, so you would need a minimum of 3 GB to run three instances safely.
They're all reliable, big brands. Go with the manufacturer of your server. Kingston claims to have the most reliable server memory.
It depends on how many players and plugins you are wanting on your server at any given time.
NLMs (NetWare loadable modules).