You do have accurate power to the CPU but not the 3.3v feed and I suspect the 3v CMOS battery is included in that part of the circuitry but the 2.8v reading is lower than the 5% tolerance at only 2.8v (actually it's in the 15% area). The reading in the BIOS is in Red because it knows there is a problem but probably does show the reading or does it? The hardware monitor does show the reading and that indicates to me that that's why it needs to be determined what is draining the system.
It sounds like it might not be possible to save your data but if you can, do so immediately.
If you can, shut the computer down. I don't like to do this but pull the plug if you have to what else can you do in this situation to get this to shut down?
Hold the On/Off button in for about 10 seconds to discharge any static charges in the system.
Install another new CMOS battery while grounding yourself to the frame: if you have a grounding clip, use it. It might sound like overkill but this is the time to help eliminate a grounding problem possibility.
Reconnect the power cord but don't start the computer instantly, wait a couple of minutes. During that time, if there is a power LED on the back of the computer, note its color: I suspect it should be green. My Dell desktop power LED is green even without the computer turned on yet. I believe my HP does the same but I don't want to shut it down to find out because this is the computer I'm using right now.
If it's green wait a while though before starting the computer, I suppose 5 minutes should be long enough but if you wait longer it might be a good idea, to see if it changes color.
If it changes color, leave it off and post back from another computer.
However if there isn't a power LED on the back of the computer, remove the side panel so you can see the motherboard LED before starting the above and follow the same concept of the ideas above.
EDIT: Do this part anyway at the start. I do not recall if the power LED on the back of the computer is equivalent to the motherboard LED. So watch both of those LED's if both of them are there.
Either way, I want to think optimistically and that the power LED will stay green.
--- BTW, how old is the computer?
Edited by cmptrgy, 06 November 2017 - 06:34 AM.