It's not the PC that is in power saving mode, it's the monitor. The message means that the video card of the PC doesn't send a signal.

So this clearly is a hardware problem. I'd start with installing another videocard. Or maybe I should say "a videocard" if you now have 'integrated graphics' (that's graphics on the motherboard itself).
If you can't do it yourself, you'll have to find either a shop to do it or a friend. And you'll have to buy a new card if it's the solution indeed. You can't do anything about that.

Kees