GA-EP45-UD3R Bootable USB hangs PC booting

[Armstrong1889]

Hello,
I have this strange issue in my old PC which have GA-EP45-UD3R Q9550 GTX280 4x2GB-800MHz RAM.

If I connected a bootable USB anytime between POST and just before starting the OS the PC will hang and will not accept any input, the only bootable USB made it through was Windows 10 and I don't know why, even bootable MB firmware install failed.

I tried the following:
1. Restored default setting of BIOS.
2. Cleared CMOS Values.
3. Disconnected all SATA cables from MB.
4. Removed and Swapped RAMs.
5. Replaced the GPU card with another(GTX 750Ti).
6. Replaced the PSU.
7. Removed all PCI cards.
(Disabling USB Storage (Legacy) support will works,but no bootable USB support)

I'm really out of Ideas here, I hope if anyone can help

Thanks in advance.

 

[Armstrong1889]

Nevermind, I was able to downgrade from F12 to F9 and everything is fine now.

Please close the thread.