my stand by option not work. I mean it enable flase. how I repair it. I install a new windows xp, service pack 2.

Hi,
If you are saying that you just installed SP2 and your PC will not go into stand-by, I would uninstall SP2 and reinstall it and try again. If you are still having trouble, download SP3 and install and see if that will work.
This would be a good time to make a slip-streamed OS CD, go to:-
http://www.winsupersite.com/showcase/xpsp3_slipstream.asp
or Google Slip-stream XP CD, and find out how to do it.

Hi,
Did you download and install SP3? If not try it OK.

in service pack 2 how I fixed it?

Abu, a long shot... when Setup was running it may not have detected correctly the power management scheme of your mb. Go into system32, rclick on HAL.DLL, choose Properties > Version tab. Highlight [lclick] Internal name... what does it list for your actual hal?
Make sure that you have the correct video card/adapter drivers.

Hi,
Please install audio and video drivers on your system and restart your machine. Everything should work fine.

Please reply...

Abu, a long shot... when Setup was running it may not have detected correctly the power management scheme of your mb. Go into system32, rclick on HAL.DLL, choose Properties > Version tab. Highlight [lclick] Internal name... what does it list for your actual hal?
Make sure that you have the correct video card/adapter drivers.

the internal name is = halmacpi.dll

Hi,
Please install audio and video drivers on your system and restart your machine. Everything should work fine.

Please reply...

I will try. and very soon I will reply.

halmacpi.dll is for your multiprocessor, advanced configuration power interface... so you should have Restart capability. Try updating your video drivers, then, so that option can be displayed correctly.