HP a808x Desktop Computer stuck in power save mode.?

This is a shot in the dark, but if you look at the back of you computer, where the Power Supply is, there 'might' be a little red switch. The main switch to turn on and off your PSU should be black with the "o" and "l" shape. Then above or below that there might be a red switch that's difficult to move.

That's the regional PSU setting. It changes the input voltage from 110 for the United States to 220 for Europe. If you're in the US and it somehow got set to the 220 voltage setting, your computer won't have enough power to boot, but will still turn on. Switching it back to 110v to fix this.

It's possible that a pre-built machine will not have this switch at all, and if that's the case then that's not the problem.

(It's very important that if you're reading this from Europe that you don't set the PSU to the 110v setting because it will fry all your hardware when you attempt to boot, but to have it on 220v in the US is harmless.)

Another possible issue is loose case-wires. If you open the side of your computer (make sure you touch the side of the case before you touch any of the hardware, so you discharge any static you have not into the parts in the computer), there should be a bunch of cables coming from toward the front of the computer. You should be able to tell them apart from the Power cables because they should be coming from around the front, not the back where the power supply probably is.

Find where these cables plug in. On custom built computers, the wires will end with a bunch of little connectors, plugged in very specific points, that you need motherboard documentation or a map written on the Motherboard to plug in correctly, but on a pre-built machine they are probably all attached together correctly to make assembly easier.

Find where they plug into the mobo and see if it's seating correctly on there. The case wires connect the power-button, power-LED lights, reset switch, Front panel USB and audio ports to the motherboard, so if they came undone, they could cause a problem, but this is probably not the issue either, because with pre-built machines like an HP, having them fall out is a lot harder.

It could also be a bad video card or motherboard onboard video card. In which case you'll have to look for buying another video card. The only way to really test this one is to pull out your video card (If you have one, you very well could have an onboard video card, which cannot be removed) and put it into another computer and see if it displays. If it doesn't that's probably the problem.

The easiest way to tell if you have a video card or not is if you open the side of your computer and find where you monitor plugs into. If it plugs into a port connected to the motherboard (The big board everything else plugs into, where the processor is and the back USB ports are attached to) then you have an onboard video device, and if it plugs into another card that's plugged into a slot on the motherboard, then you have a video card.

Even if you have onboard video, you can still buy a separate video card and install it, and if you card stopped working the good way, you should be able to just replace it. It's possible that it could have done further damage when it went and ruined you whole computer, but it's possible the video card isn't even the problem.

Without actually seeing the computer, that's all I can tell you to try. If none of this works, you might want to take it to a repair place, or ask a tech savvy person you know to come take a look at it. Try to avoid Best By Geek Squad, since they have no idea what they're doing and overcharge a massive margin for doing practically nothing or literally doing nothing.