"Protect" means that the unit is seeing a short at the speaker outputs, either internally or externally and it is protecting the rest of the circuitry from further damage.
Try unplugging the unit for 60 minutes, then plug back in and try it again. This will reset the processor and hopefully the unit will operate normally. Check all the speaker wiring for shorts, make sure they're also not touching the chassis of the receiver, or are not otherwise pinched or frayed. If all looks well, try disconnecting all the speakers and cycle the power off, then on again.
If it powers up, try connecting the speakers one at a time until one of them shuts the receiver down. Check this speaker with a multi-meter and make sure it is reading between 4-8 ohms. If not the speaker may be blown and is causing the receiver to see a short and therefore power down.
If the unit shuts down with no speakers connected, or shows "Protect", then it has a bad output transistor, or capacitor and is in need of service. I can send you the contact info for a Service Center near you if you'd like, but typically it is not worth it to repair these devices.
Sorry about that, there's no way to tell what the skill set of the person asking the question is. Chances are the "protect" means that the Sony is shot and needs to be serviced, but the cost of repairs usually exceeds that of a new unit. The only thing you can do to find out if it's a problem with the Sony, or a blown speaker causing the problem, is to disconnect the speaker wires (all of them) at the rear. Make sure you use a piece of tape on each one and label where it plugged into- doing this AS you disconnect them one at a time). Once all the speakers are disconnected, try turning the Sony back on again and see if it still says "Protect". If it doesn't, then the problem is with one of the speakers. If it does, then the problem is with the Sony itself.