Declaring the results of my trial attempts. Everybody will love to see that, however it was so late at night that I preferred to post my result in the morning, so apologies for the delay. Following are the steps :-
# I removed the battery from the board as suggested by Sylvia.
# I opened the processor fan, opened the casing (I did it for the 5th or 6th time, although all on my previous attempts), took out the processor, inspected the assembly, cross-checked with the integration guide. Everything seemed to be absolutely fine. I assembled it once more, applied some thermal paste this time as I felt that the pre-applied paste might have lost some of its properties, and put the fan and everything in its position.
# Waited for about 2 hrs, the reason why I was so late at night.
# This time decided to test everything outside the cabinet,(the same is suggested in the troubleshooting steps in intel site), so kept the motherboard on wood covered with soft packing board that came with the cabinet.
# Checked the cabinet start switch, the continuity testing with multimeter suggested that it was working perfectly OK.
# After 2 hours, connected power connectors in my mobo, put the battery back to its position, took the RAM out of its slot, and switched on power. Three beep sound came from the mobo.
# After disconnecting power supply, the RAM was put back in its position, and switched ON the PS. This time the fan started, the proc. temp. LED turned on for a sec. and immediately turned OFF. I was staring at the monitor, however, the processor fan stopped. One major difference was that this time the processor fan started with good speed unlike other times when it barely managed to take a quarter turn and immediately stopped.
# The system was running on minimum hardware, on 4 GB RAM and the monitor connected with the DVI cable, and a 500 GB Sata hardisk.
# A little frustrated, I pressed the start switch for 4 to 5 times, this time the processor fan started, never stopped, and the intel symbol appeared in my monitor. (Just had the feeling that I have done some Newton job, only the apple was missing). Loaded Win 8 OS, the OS loading was successful.
# Switched off the power supply a couple of times and switched it ON, every time it was a nice start without any hitches.
# I assembled everything inside the cabinet and now, the system was running perfectly.
My sincere thanks and regards to Al_Hill for putting the post in right location, to Sylvia for your valuable suggestions which got me through, and thanks to Hemant for all your efforts.