My computer suddenly turns to "Power Saving Mode"

[asianman]

This happens whenever my computer encounters "Bootmgr is missing". After fixing up that problem, when I let my computer around 5 minutes, it goes to "Power Saving Mode". I have checked the settings at power management, and I never set my computer into that mode. I also replaced my monitor with another one, but it appeared the problem is still persist.

Appreciate your kind advice and solutions for this problem.

Thanks.

 

[AddRAM]

Desktop or laptop ?

What Model ?

 

[asianman]

Desktop.