memory not properly reported

I have a computer running windows xp service pack 3, I have 2 memory modules of 512mb each. My bios settings report 512mb in bank 1,and bank 2,which is ok, but when I check system properties it indicates only 512 mb of ram. I verified the video ram is 8 mb according to the bios set up.My question is why is the operating system reporting only 512 mb of ram when I have 1gb installed ?
Thanks for any help offered.
Billy

 

If you have already verified both your cards are good and you have more than 2 slots, try moving your cards to the other side (install your cards from the left if they are on the right or viceversa). This happened to me a long time ago in an older box I had...

 

I would suggest you switch off your comp and open the case and carefully eject the RAM from slots and clean and reinstall, making sure they are fully seated. If they don't show after restart of comp, switch off and change RAM from one slot to the other.
I've experienced this before and it's usually the RAM not seated fully or dust/dirt. Cheers Neil.

 

what does the bios report on bootup
enter your bios control panel on bootup and read what it says
Then you can rule out if the problem is in windows itself or not