Power saving mode has been designed in computers to save energy when there is no activity for a prolonged period or if the power source is not supplying power. In the case of laptop computers this could also be down to an empty battery. If users face a scenario where their laptop computers cannot exit from the power saving mode, then it is problem with the battery located on the motherboard. The only solution for this is to replace the battery with a new one and then restart the computer.
My computer does in power saving mode at completely random times; my screen goes blank and it says "Entering Power saving mode" after which the green power light on the monitor changes to orange. When I try and exit the power saving mode, either by pressing keys on the keyboard or move the mouse, nothing happens. Pressing any power button (or monitor button) doesn't help either and the only thing I can do is hold the power button to shut my computer down and reboot it.
When you cannot get a computer out of "power save mode" by any other means, typically the cause is that the battery of your computer, which is located on the motherboard, is empty.
The motherboard battery is used to store various settings when the computer power is off, such as date and time. When your computer detects this battery is empty, it goes into a low-power mode.
The solution is to replace the battery:
Open the case of your computer;
Locate the motherboard (the main electronic circuit board) of your computer;
Look for the battery (it looks like a digital watch battery, but a bit larger);
Get the reference and buy a new one from a computer shop and replace it
Restart your computer: it should now power up normally (you may get some warning messages during the start-up sequence, but ignore them);
Set the date and time on your computer using the "Date and Time" control panel;