Somebody once asked that they can't see all of the 4 GB memory (RAM) when running standard Windows XP (32-bit), but the same is visible in Windows XP (64-bit). The reason for which is, the standard version of Windows XP is a 32-bit operating system. Its only the newer computers that are provided with the 64-bit version. In 32-bit mode, the maximum amount of memory which is visible to the operating system is 4GB. For instance, if you have a 4GB RAM and 1GB video card on your PC, Windows XP would ignore 1GB RAM to make 1GB of video card visible. So the total amount of memory Windows XP 32-bit would report under "My Computer" is 3GB. "My Computer" doesn't include memory reserved for the video card in total. If your computer has devices which require even more memory to be sacrificed, the total amount reported for the RAM would drop down further.