If you upgrade your RAM to 4 GB and check the system information box to see how much memory you have, you will find that it only says three gigabytes. This is true if you have a 32-bit processor. Does this mean something wrong with the chips in your computer?
Even though your computer’s motherboard may support 4GB, your OS may not report the full correct amount when you check the amount of RAM installed on your system. This is because, some of the memory gets allocated to support hardware devices such as the graphic card and network components. This memory is not displayed by the OS.
On some computers, the correct amount of memory will get displayed if you install Windows Vista Service Pack 1. This is because Windows Vista Service Pack 1 reports the exact amount of memory installed and not the amount of memory that is available to it.
32-bit operating systems do not support more than 4 GB of RAM. However, 64-bit operating systems can handle more RAM. For example, the 64-bit edition of Windows Vista Home Premium supports up to 16 GB of memory while Windows Vista Ultimate supports 128 GB of memory.
64-bit processors can handle more memory as they have a wider address-bus. However, you will need to install a 64-bit OS to take advantage of the full capabilities of the processor. 64-bit processors offer higher computing power and allow you to run more number of applications at the same time.
If your RAM chips are damaged, you will observe frequent crashes. In some cases, your computer may not even boot. In such cases, you will have to take the help of a computer repairman or replace the memory.
You can test your RAM by downloading Windows Memory Diagnostic utility from http://oca.microsoft.com/en/windiag.asp or MemTest from www.memtest.org or http://hcidesign.com/memtest/.