Hey guys, I'm having a weird issue here that I have no idea how to fix. Every time I go to turn on my pc the next day, it won't boot unless I switch it off first - but that's not the whole story. I once tried switching off the psu before turning it on (again, a day later) and it still wouldn't boot. No image is sent to the screen, there's no hard disk activity, but once I try it again (usually after having switched off and on the psu, since it won't shut off after the first time I boot it) it works perfectly. Nothing is overclocked, the system is otherwise extremely stable and I usually have it on all day, before switching it off at night. Components are as follows - i5 4690K 16GB Asus Z97P motherboard MSI Radeon 390X EVGA SuperNOVA 750 G2 PSU The processor and motherboard are relatively new, having been bought back in May, while the PSU and graphics card are newer still, going back to early July. I initially did not have this problem when the components arrived, and everything was running perfectly. I had Windows 10 installed cleanly, after an upgrade from Windows 8.1, but something odd happened when I booted one day - Windows reported there was some error. It said it was fixing that error, rebooted twice, and seemed to be back to normal. But it wasn't back to normal. Things kept happening when before they were completely fine. The display driver kept crashing, for one example. So after a few days of dealing with a somewhat badly behaving OS, I decided to go back to Windows 8.1, reformatting and doing a clean install. Once done, the pc now runs perfectly stable, and some things are noticeably (and weirdly) better than before - my 390X now runs cooler, for some reason (before it would go up to about 73c degrees and then slowly climb down to 41, now it never runs hotter than 60c and idles on the desktop at 29c... I've even see it go down to 26c. I've run stress tests on the processor, ram and graphics card. Everything is running perfectly, with no performance issues, or indeed issues of any kind. But for the booting issue. I have updated my bios to the latest version, and have found nothing in it to suggest this weird behaviour (and I have changed nothing since my original Windows install anyway). I have noticed that my headset light will stay on when the pc is off while the lights on my keyboard and mouse will be off, but I don't know what to make of that (the headset light only goes off when I switch off the psu). The pc is not overclocked in anyway, and was not when Windows 10 was running. So, I have no idea guys, and if anyone has any suggestions, I'd be very grateful.