Computer does not show all installed memory capacity
Cause: Do you use on-board graphics? If yes, then the graphics will share memory from the system RAM, since it doesn’t have its own. If the installed module is dual-banked and the system board only supports single-banked memory, then the computer will read and use only half the installed memory. Older machines have a limitation on the amount of system memory. If the limit is crossed, the additional megabytes go unrecognised.
Solution: Find out (from the BIOS setup under Advanced Chipset Features) how much MB of the system RAM is allotted to on-board graphics. Now compare the remaining amount with the amount displayed by Windows. If the count does not match, then restart the system and check with the BIOS/CMOS setup for the memory count. Failure of the BIOS to detect the entire capacity indicates incorrect choice of hardware. Refer the motherboard manual or site or dealer for suitable specifications.