Thanks Hack. This is the solution:

Code:
using System.Runtime.InteropServices; // To use Dll import.

....

[DllImport("kernel32.dll")]
		public static extern void GlobalMemoryStatus(out MemoryStatus stat);

		public struct MemoryStatus 
		{

			public uint Length; //Length of struct
			public uint MemoryLoad; //Value from 0-100 represents memory usage
			public uint TotalPhysical; // The total RAM.
			public uint AvailablePhysical; // The Available RAM.
			public uint TotalPageFile;
			public uint AvailablePageFile;
			public uint TotalVirtual;
			public uint AvailableVirtual;

		}

......


MemoryStatus MemStat = new MemoryStatus();
GlobalMemoryStatus(out MemStat);


......


Console.WriteLine(MemStat.TotalPhysical/1024/1024.ToString());

...// To access available RAM, MemStat.AvailablePhysical

Jennifer