Thanks for the response
I used Original XP Professional SP2 and have used different cds for installation.
The sound device is on the motherboard - Yes.
This problem is even with the newly assembled systems also.
I have tried it even with slipstreaming xp3 and slipstreaming mass storage drivers for sata hard drives.

Dear Friends, I am starting this new thread after having failed in all my attempts to solve this problem.  After installing everything in windows xp sp2 professional drivers etc. using  latest driverpacks after using computer for about 20 -25 minutes the sound goes off.  The volume slider in control panel sound properties goes dimm and nothing can be done.  I have felt that after this the internet also does not work.  I have to restart the computer again to listen to the sound.  Please help me solve this mystry.  If anyone have faced the same problem and have any solution.  Thanks in advance