Using standby mode, is supposed to save energy when your PC is unattended, and help your Monitor last longer. In other words it switches over to using a screen saver if left unattended for a while.
However, this facility can cause problems, because sometimes when you try to bring back your 'normal' screen you find your PC is frozen. No mouse, no alt/ctrl/delete function ...
Nothing....
Then you have to switch off your computer (even that doesn't work sometimes), reboot and run scan disk, just to get back to where you were before you took time off for that cup of coffee.
If this has happened to you, the answer is to disable the standby mode. Here's how ...
RIGHT Click on a blank area of your desktop.
LEFT Click on / Properties / Screen saver / Settings (or Power)