Hi Arijit_mitra,
Thank you for visiting the HP Support Forums and Welcome. I would be happy to assist you. I have read your thread on your HP Compaq Presario Notebook and LED issues. Here is a link to connecting a monitor.
If you connect an external monitor and all is well then the issue is with the LED on the notebook. Here is a document for hardware test. It will let you know if there are any issues you should be aware of in the hardware of the Notebook. If all comes back with a pass, I would try a system restore.
I would be happy to assist if needed. How Do I Find My Model Number or Product Number?
Please respond with which Operating System you are running:
Which Windows Operating System am I running?
Please let me know.
Thanks.