Hi, Today I installed 4GB of ram and in bios it detects 4096MB and when I am in desktop right click on my computer it shows as 2.5GB of ram??? Why is that:? Is their any solutions for this? Will it fix if I install windows xp 64bit edition?
It's a 32 bit problem, 32 bit systems simply cannot address that much RAM. To quote hitman012 of bit-tech.net forums: You will only ever be able to use the full four gigabytes with Windows XP 64-bit edition. The maximum addressable limit of any 32-bit operating system is 2^32 bytes, or about 4GB. However, much of this is actually reserved. Modern computer systems use a technique called memory-mapped I/O, whereby CPU-addressable memory space is actually reserved as a means of communicating with I/O devices. These devices monitor the CPU's address bus and direct any operations performed on the MMIO area to their registers, effectively remapping the section into peripheral memory. To save time and money, it is not actually possible to bank switch this area between memory and device addresses, so it's effectively unusable. However, if you're running a 64-bit processor and operating system, you can activate an option in your BIOS (usually PCI MMIO remapping or Remap Memory Hole Above 4G) that moves this MMIO area above 4GB to allow you to use the complete RAM capacity (note that you can activate this option without running a 64-bit OS, but it probably won't do anything). There is a way to enable access to a bit more than normal on XP by modifying some configuration data (AFAIK it's the /PAE (physical address extension) switch), but ultimately you will never be able to access all of it unless you switch to XP64 or an equivalent Linux distribution.
