i have a self build computer spec as follows via motherboard,amd athlon xp 2200 chip,80 gig hard disc,nvidia gforce fx5200 agp graphics card 2x256 ddr pc2700 ram sticks with xp home with sp2 when i start my machine and check my computer properties it shows the full 512 mb of ram, but when the machine has been running for about half an hour the properties show384 mb of ram, it causes no problem but i would like to know where the other 128 mb of ram is going any advice would be very welcome

Is this a new problem? Were things working OK previously?

You might want to test your RAM: http://www.memtest86.com/

memtest checked out ok any more ideas

system works ok its always done this just wondered what is holding on to the memory

Try this little app: http://www.cpuid.com/cpuz.php

Look under Memory and SPD for any clues.

Does your motherboard have on-board VGA? If so is it disabled in the BIOS?

CPU-Z Report

--------------------------------------------------------------------------------

CPU-Z version 1.35.


CPU(s)
Number of CPUs 1

Name AMD Athlon XP
Code Name Thoroughbred
Specification AMD Athlon(tm) XP 2200+
Family / Model / Stepping 6 8 1
Extended Family / Model 7 8
Package Socket A
Core Stepping B0
Technology 0.13 um
Supported Instructions Sets MMX, Extended MMX, 3DNow!, Extended 3DNow!, SSE
CPU Clock Speed 1794.9 MHz
Clock multiplier x 13.5
Front Side Bus Frequency 133.0 MHz
Bus Speed 265.9 MHz
L1 Data Cache 64 KBytes, 2-way set associative, 64 Bytes line size
L1 Instruction Cache 64 KBytes, 2-way set associative, 64 Bytes line size
L2 Cache 256 KBytes, 16-way set associative, 64 Bytes line size
L2 Speed 1794.9 MHz (Full)
L2 Location On Chip
L2 Data Prefetch Logic yes
L2 Bus Width 64 bits



Mainboard and chipset
Motherboard manufacturer
Motherboard model KT400-8235,
BIOS vendor Phoenix Technologies, LTD
BIOS revision 6.00 PG
BIOS release date 02/10/2003
Chipset VIA KT400 (VT8377) rev. 00
Southbridge VIA VT8235 rev. 00
Sensor chip ITE IT8705




Memory
DRAM Type DDR-SDRAM
DRAM Size 512 MBytes
DRAM Frequency 133.0 MHz
FSBRAM 1:1
DRAM Interleave 4-way
CAS# Latency 2.0 clocks
RAS# to CAS# 3 clocks
RAS# Precharge 3 clocks
Cycle Time (TRAS) 6 clocks
# of memory modules 2
Module 0 Nanya Technology DDR PC2700 - 256 MBytes
Module 1 Nanya Technology DDR PC2700 - 256 MBytes



Software
Windows version Microsoft Windows XP Home Edition Service Pack 2 (Build 2600)
DirectX version 9.0c

this is a copy of report

yes on board graphics are disabled in bios

In some BIOS (probably under Advanced) there is a setting for Video Memory Sharing. Even tho the on-board VGA is disabled the BIOS still might be set to share RAM.

If you cannot find such a setting then my RAM sharing theory is finished.

Will continue to search for other ideas.

Also (just for the why not) try this scan:

http://www.d-a-l.com/hardware-scan.php

under advanced chipset settings it has a agp aperture size setting which is at default value of 128 mb i have a 128 mb agp graphics card installed

This is designating 128 of your RAM to the AGP card above and beyond the AGP's own memory. Setting this to zero will give all your RAM back to the Operating System.

The reason for writing this guide is that many people still ignore the importance of AAS or set it incorrectly. Generally measured in megabytes (MB), AAS is the amount of system memory (RAM) shared with an AGP graphics card in order for it to have more memory to process textures and other visual data.

Some people think that the more RAM you share with the graphics card, the larger the performance boost. In some cases, this might be true. In others, it might result in a performance drop. There are two common outcomes from setting the AAS too high: (1) If you share too much RAM with your graphics card and an application takes advantage of that, you will have less RAM for other functions of the software, and possibly for background applications. (2) If the graphics card does not utilize the memory, it is not taken from system memory. In this case, there are no problems with AAS sucking all of your system RAM, despite its setting in the BIOS configuration utility. The latter is the most common case, since most people have enough memory now to compensate for a high AAS, and most applications would not take all of the memory anyway.

http://www.tweak3d.net/articles/aperture-size/

that seems to have solved the problem thanks for your time and advice