My PC stopped booting (including no graphics on screen). I stopped it (pressed the power button for 5 secs). It restarted and started beeping three times once. I cleaned up the RAM and it didn't beep but neither succeed to boot. I noticed by chance that it only boots up after turning the source off and turning it back on. What's going on ? should I replace the battery ? Is the mobo leaving its last days ? Is the RAM bad ?