Last night, I was in a hurry so I shut our PC down by pressing the power button for more than 5 seconds. I normally don't do this...
Anyway, this morning, when I tried booting the PC up, I was greeted by a "Insert boot media and press any key" screen. I went to BIOS and there it showed that my SSD (which contains system OS) isn't recognized.
After scouring the web & trying various solutions, this is the only one that worked:
1) Ensure PC is off
2) Remove power & SATA cables from SSD
3) Put power cable back into SSD
4) Turn PC on; eventually "Insert boot media and press any key" message will be displayed
5) Leave PC on for 20 minutes
6) Then connect SATA cable into SSD (yes, SSD is still powered)
7) Then push RESET button in your PC; don't turn PC off, just the RESET button
8) SSD should be back in business at this stage