I have a Gateway DX4860, Intel Quad I5, INTEL MB DH55HC w 12G RAM, Windows 7 SP1. All data backed up. I want to clean install from Windows 8.1 (Full Version). Gateway recommends BIOS update before Windows 8.1 install. (Current BIOS, P01.A2 of 04/07/2011) doesn't support UEFI). Gateway provides a BIOS upgrade flash program to P11.A3 of 9/2/2013 with optional UEFI support. The installer stops before executing with an error message that reads "ROM file size does not match existing BIOS. Gateway tech support is horrible. Help!