When I opened up my laptop after few days, I could see red vertical lines on my login window, and the PC hanged. I tried restarting and booting up many times but nothing helped.
I cleaned my laptop and tested the RAM and HDD. Both test were successful. The fan heated up too much, but is now clean, and hence the fan runs OK.
I then reformated my PC with an HP OEM CD (as I have an HP laptop). I restored it to the original factory settings.
The factory settings (restoration) completed OK. When the computer said "Preparing computer for your first use" again those red lines were still visible on those text.