Hi--
The Windows install disks are images downloaded through our University Site license. They work fine on these 800 G1 boxes if booted from bios to the CD, but as I noted, not if booted from UEFI. Yes, I've tried F9-- force to bios CD rom-- windows install disk boots; force to UEFI CD rom, Windows install disk does not boot. Disk gets read, then stops.
The point, here, is to use Samsung SSD memory and bit locker using the intrinsic encryption of the SSD. Much faster and easier to use bit locker (to encrypt and unencrypt is instantaneous) and this all works fine on the 8300s.
I'm pretty sure that you cannot switch from a bios booted machine (one in which you loaded Win 8.1 from a bios boot) to a UEFI booting machine.
I have not tried updating the bios, yet. Can try that. But I assume that no one has successfully loaded Win8.1 on the 800 G1 machines using UEFI.
I've tested two 800 G1 machines so far. None will boot the windows 8.1 install disk from UEFI. I don't have time to test more machines-- I was going to wait for others to be affected by this and for HP to come up with a fix.