hi..........i am prabhukumar.each time i turn on my system i am getting an that "CMOS settings wrong.press f1 to run setup f2 to load default values and continue." please help me.................

That typically means the battery is bad. Replace the battery as per your motherboard/computer instructions, boot into the BIOS setup menu and set date and time, then save and exit. It should then boot normally. If not, you have other, more serious problems.

can u please tell me how to replace the battery for asus p5g-mx motherboard?

1. Power down the computer AND UNPLUG from the wall.
2. Open case side panel.
3. Touch bare metal of case interior to discharge any static in your body.
4. Locate motherboard battery - looks like a small silver coin.
5. Note polarity of battery - typically the positive + side is up.
6. Pry out battery with non-conductive tool - strong fingernails work for me.
7. Take battery to store - most battery/camera/watch counters will have replacement. It is typically a CR2032, or suitable substitution. Most counters will recycle old battery.
8. Do NOT touch new battery with bare fingers - skin oil promotes corrosion and attracts dust. I put a clean sock over my hand.
9. Touch bare metal again.
10. Insert new battery, observing proper polarity.
11. Clean interior of case of heat trapping dust.
12. Inspect all cables to insure securely fastened.
13. Close case and connect power.
14. Upon first boot, go directly into BIOS Setup Menu by pressing the Del key when prompted during the early stages of the boot process
15. Reset date and time and verify drives are properly identified, and boot order is as desired
16. Save and Exit to boot normally.