If you are sure these changes happened by themselves you may want to replace the CMOS battery...



Part # CR 2032 available almost anywhere.
As always when working inside the case remove all power and take anti-static precautions.
Be careful not to break the spring clip that holds the battery in place.i removed the RAM sticks clean & reinserted. but still the problem persist.Follow Patio's suggest too.i replaced the CSOM battery, but still same problem. should i shift the two RAM chips to other slot? why this problem occured?The only things left I can think of are that either the motherboard is going bad or the memory is.I am using 2 memory sticks of 256 DDR RAM chips. (Total – 516 MB). I tried to boot computer using one by one. I found that computer is not booting with one of the RAM sticks. This may be is creating the problem. If I want to replace the sticks, which one the latest RAM should I buy which will fit in my motherboard? There r four slots for RAM in my mother board.The computer was booting with one and not the other?

You can check www.crucial.com or www.intel.com for information about that board's memory capabilities.

If I remember right from the two I have of that model:

DDR266 if system bus is 800MHz, 533MHz, or 400MHz
DDR333 if system bus is 800MHz or 533MHz (gets underclocked to 320MHz)
DDR400 if system bus is 800MHz

The memory information for that board can be found HERE
I just verified the information about speeds there. Surprised I can still remember that, I've had these boards for years. Anyway, check that page for more complete information and check your bus speed.thanx all of U for ur expert advice. but when i make the power on the computer starts directly without pressing the power button & the screen of BIOS setup UTILITY comes. how to solve this problem.I seem to remember my D865PERL boards (one of them at least) doing that at one point. Can't remember of the top of my head why. Might be the BIOS setting about rebooting after a power failure. it OK now, only it gives messege that it is running on single RAM. will change new RAM soon. thanx any way.i changed the defective RAM with another 256 MB RAM stick, BUT NOW IT IS SHOWING MESSEGE DDR 320 OPERATING IN SINGLE CHANNEL MODE. may both RAM sticks not matching?They need to be a MATCHED pair and installed in every other slot DEPENDING on the board layout...