Windows Server 2012 Standard - 0x00000091 on boot

I've been attempting to install Windows Server 2012 Standard on some relatively (circa 2007) old hardware. The machine itself is an Intel SE7320EP2 based system running 2x Dual-Core Xeon (64bit) processors. I initially got the 0x000000C4 error upon attempting to install, subsequently I found the fix which invoved updating the BIOS to the latest firmware and then enabling the NX/XD bit.

So after this I got the following message (after the initial installer load):

Your PC needs to restart.
Please hold down the power button.
Error code: 0x00000091

I then tried installing Windows Server 2008 R2 SP1, which worked without issue. Bingo I thought, I'll do an upgrade to 2012, it's sure to tell me about any hardware issues if it's an upgrade-installation with drivers already loaded.... wrong!

Windows 2012 went through its upgrade/install/update process, then upon reboot the 2012 splash-screen came up, woo! It's working (I thought), hard-drive span a few cycles and then we're back to the old:

Your PC needs to restart.
Please hold down the power button.
Error code: 0x00000091

Does anyone know what the 0x00000091 is related to? I've done some google searching but can't find anything beyond vague references to hardware incompatibility. I know the H/W itself is around 8-9 years old now, however I can't understand how 2012 fails to boot where 2008 runs fine (given they both use 64-bit architectures etc etc...)?

Any answers much appreciated!

Windows 2012 requires newer hardware than 2008. The error 0x00000091 is usually the result of a hardware failure or unsupported hardware.