So ive bought a new pc 1 year ago and it worked properly for about 6 months... then i had the boot disk failure but only sometimes. Everything was set up right in the BIOS. After i got sick of it because it slowly got worse after time ive decided to get a new Hard disk and the Problem was gone. And now, when i leave my PC on idle for about 30 minutes it automatically restarts and it says Boot disk failure again... so is it my power supply or mainboard?