PC was in use, SUDDENLY in CPU all indicators & fans switched off, Monitor blank, But Num lock on keyboard was on & mouse light was on. After hard RESET only mouse light getting on.Hi, peearekay

My first thoughts point to a failing power supply. If you are comfortable with opening up your computer and you have a known-good power supply lying around then you could use it to test. If you don't have another power supply lying around then you could borrow one from another PC you have or a friend. (As long as it is compatible with your motherboard). Open the side of the broken PC and disconnect the main power from the motherboard (20 or 24-pin "EGG crate" connector). There is typically a 4-pin power connector also that should be located near the CPU, disconnect this as well. Then plug the main board power connect and the 4-pin power connector from the known-good power supply into the board. Plug the power supply into the wall and fire it up. (be sure that the switch on the back of the known-good power supply is switched on if it has one).

If the machine FIRES up and works then you know it is time to buy a new power supply! If not, then you may be looking at something more serious such as a motherboard.

Good luck!

Mike

There might also be some instances where some of your hardware must have just moved a bit.

Try removing the RAM cards and put it back in PROPER place again.

That was the case for me a few months back.