|"I have tryed other PS on same motherboard, And it continues to not work. "|
That doesn't necessarily prove the mboard is the culprit !
See response 12 !
"Using a nvidia geforce gtx 550 ti for graphics."
Minimum power supply:
400 watt or greater with a minimum of 24 amps on the +12 volt rail
Some power supplies have more than one amperage rating at +12 v because they have more than one +12 v section on the PSs board - if so, add them.
If the 400 watt PS you used doesn't have at least that total amperage at +12 v,
or even if it does if it's an el-cheapo PS that rating may be a lie
- in that case your mboard would probably NOT BOOT when that video card is installed, even when there is nothing else wrong !
Try your 650 watt PS with a working computer !
"The Machine Died while I was sleeping,"
If it was running, WHY was it running while you were sleeping ?
If it was not running, you did NOT need to have live AC power going to it.
It's possible there was a power failure event while you were sleeping.
That can produce power surges or voltage spikes that can damaged the computer or anything attached to it, especially if it was caused by lightning strikes.
"No change as per expansion cards or anything else within 1 month. Only difference I did was put my tower on my desk instead of the floor."
Sometimes when you move a computer connections inside the case get loosened and something is not making a good connection.
Unplug the case/power supply, or switch off the AC power to it otherwise.
Power off your monitor.
Open up the case. Check all the connections of the wiring to make sure they are all the way onto their pins and into their sockets, especially the main connector from the power supply. The wires close to the mboard going into the main power connector / socket should be more or less perpendicular to the mboard surface rather than at an angle. Make sure all cards in slots are all the way down in their slots. Make sure all ram is all the way down in it's slots, and that the latches at both ends of all the modules are against the ends of the modules.
Make sure that there is nothing metal that is loose inside the case that may have moved when you moved the case that may be shorting something on the mboard, or underneath the mboard. If you pick up the case and shake it, if there is something metal loose you will probably hear it moving.
This isn't likely since the mboard was working previously, but we have rarely seen this situation even when it had been working previously ....
- make sure that you do not have metal mounting posts in positions behind the mboard where there are no mounting holes in the mboard.
"The motherboard may well be defective but your logic as to why is faulty."
I certainly agree with that.