Thanks all for very useful suggestions. Tried with bootable disk of OS and AV but the machine won't budge.

Since it is not covered under any warranty anymore, therefore, yesterday took it to a repair technician. His final verdict: it cannot be repaired. The only option he gave me is to format the hard drive and reinstall the OS. Now he is working on data recovery.

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Man's Best Friend

YoursTruly --

Your very likely problem is the installation of XP Service Pack 2.
Did you start having problems after SP2 was installed?
If so, then that's the culprit.

SP2 has so many problems in it that it is better not to install it.

Does your laptop have a floppy drive?
If so, try booting with a DOS floppy and see if you can run the anti-virus from the command line.
Or try and run the repair command from the command line.

Other than that, if the machine doesn't boot - there is only one option left - wipe it clean and start fresh

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"Mah deah, there is much more money to be made in the destruction of civilization than in building it up."

-- Rhett Butler in "Gone with the Wind"