After attempting a BIOS update using HP's windows executable, my HP Pavilion Elite m9515y now refuses to boot from any device, external or internal. When attempting to boot from internal HDD, USB Flash Drive, or CD/DVD it will always show a black screen with a white cursor in the top-left blinking indefinitely. Because of this, I've been unable to boot into any diagnostic utility or recovery environment. I suspect that the HDD is fine and probably still bootable, as I've tried my bootable flash drive and dvd on other computers successfully.
In troubleshooting this issue, I have attempted to reset the bios via MoBo jumper and by removing the Cmos battery for 15+ minutes while the PC is unplugged. This succeeded in restoring default BIOS settings but not in allowing the PC to boot to any device. I have been unable to locate an OEM version of the BIOS to flash, only HP's executable update, and I'm not even sure how I would flash the BIOS without being able to boot to a device.
Any help would be, well, helpful!
MoBo: MS-7548 Ver 1.0
PC Model: HP Pavilion Elite m9515y
All default hardware but CPU fan, which was recently replaced with an Antec 80mm LED fan. Thermal grease on CPU heat sink was also cleaned/reapplied in the last month due to high fan speeds and minor heat management issues.