Setup Installation :: ASUS M2N-E Won't Boot Win 8.1 After BIOS Update

It has an ASUS M2N-E motherboard with an old single core AMD Athlon 64 (I cannot remember which model specifically).

Last week, I provided him with a couple of old HDDs and 8GB worth PC-5300 DDR2 667 MHz RAM. We also installed Windows 8.1 64-bit, and other than the CPU being a single core and a bit slow, things were proceeding relatively smoothly.

He has an NVIDIA Geforce 8500 on the board, and he's ordered a PNY-made Geforce GTX 650 that's on it's way at present.

He's wanting to upgrade the CPU to the AMD PHENOM X4 9950, so we've been periodically meeting over the past couple of weeks to perform surgery on this old machine.

At any rate, we found that to update the CPU, we needed to update his BIOS from the one that was installed, which was at revision 0502. The needed BIOS revision for the CPU was 1504, but would also work with revision 1701.

After jumping through several hoops to update the BIOS, we updated it to 1701. However, since then the machine will not boot into Windows 8.1. He gets an instant BSOD. I did not see the error code, so I cannot say what it was. He told me that he's attempted to do a repair install to no avail. The repair attempt results in a constant loop of the machine rebooting and BSODing.

At any rate, here are some URLs that detail the board specs and the list of BIOS revisions for that board.

Motherboard Specs: Motherboards - M2N-E - ASUS
CPU Compatibility list: ASUSTeK Computer Inc. -Support- CPU Support M2N-E