my pc wont turn off and no signal to the monitor

[goranCRN]

(when i unplug the power suply and plug it again i turns on instantly)and get no signal to the monitor.i havent been touching the hardware, it just happend...

 

[Dimitar_Grigorov]

In most cases this symptom means that your motherboard is broken. The other cause can be stuck power/reset button.
To confirm that your motherboard is OK you need to replace almost every other part with working one. Most technicians start with the power supply, then they clean then RAM slots and the CPU socket. After that they reset the BIOS etc...