0x80070570 on 8.1 Clean install from USB

OK, so I'm having this issue with Lenovo G500 (500+8GB SSHD, 4GB RAM, UEFI). I'm trying to install Windows 8.1 (x64) on this laptop for three days now. I tried different methods for creating a bootable USB drive (Rufus, WinToFlash, manual), in both UEFI and BIOS (Legacy) modes, both got me a 0x80070570 (missing or corrupt file). I have the official ISO from Microsoft DreamSpark and I tried...