My PC (Gigabyte GA-Z77M-D3 & Intel i7 CPU) has been working fine with the Windows 10 upgrade since a month. Today (31/Aug 2015) I tried with the boot manager to start from an old XP HD (it was working with Win 8.1). As it didn’t work I changed the BIOS default from SATA to AHCI. Still no luck and suddenly it was starting from the Win 10 HD saying that it was attempting Automatic Repair. Since then all went wrong. The PC turns ON and OFF without the screen for 4-5 cycles then on the 6 ot 7 cycle I got the BIOS screen but couldn’t enter BIOS settings (Del) even with a PS2 keyboard, following this I could see the gigabyte dual bios UEFI logo on the top and nothing else. I tried resetting times the BIOS (Clr CMOS & battery off) many times, removed all cards, new RAM, new PS and now it won’t even start the power supply.
I AM CONVINCED WIN 10 CORRUPTED THE BIOS/UEFI SETTINGS. I will try to get my motherboard re-flashed/repaired.
(I have read some post with the same issue)