Why doesn't my Windows® PC recognize the whole 4GB of memory I installed?
In a 32 bit operating system, if you installed a total of 4GB of memory, the system will detect less than 4GB of total memory because of address space allocation for other critical functions. Some of the functions that use the undetected memory are listed below:
- Motherboards resources
- Configuration for AGP/PCI-Ex/PCI
- Other memory allocations for PCI devices
- System BIOS (including motherboard, add-on cards, etc..)
- Memory mapped I/O, such as USB ports
Different onboard devices and different add-on cards (devices) will result of different total memory size. E.g. more PCI cards installed will require more memory resources, resulting of less memory free for other uses.
This applies not only to desktops but laptops as well. The only way to get around the limit imposed by Windows would be to upgrade to the 64bit edition of the operating system (which requires a 64bit processor).
To determine which version of the Windows operating system currently is installed please follow the instructions found through the link below. http://support.microsoft.com/kb/827218