I know most of you won’t care about this, but if you own one of HP’s marvelous little servers this is useful information.
I have two of these devices in my office. They are reminiscent of the old HP Home Servers, except much more solidly built. They are quiet, have four easy-to-access SATA drive bays, and at a list price of approximately $350 are quite affordable. If you’re a patient buyer it’s possible to find this model or its successor, the ProLiant MicroServer N54L, on sale for under $300. (I paid $250 each for mine, in 2012.)
For the past year, one of my microservers has been running Windows 8 (acting mostly as a media file server) and the other has been running Windows Server 2012 Essentials, performing backups and acting as a business file server and remote gateway.
After the RTM releases of Windows 8.1 and Server 2012 Essentials R2 became available, I tried upgrading both machines—and failed miserably. The upgrades went OK until the first boot, after which the system hung and refused to complete installation. I applied every update I could find, with no luck. So even as I upgraded every other Windows device in sight, these two remained stuck on last year’s software.
As it turns out, I wasn’t alone. This thread on Microsoft’s support forums turned up multiple examples of people who had been burned by the issue. I found some more on Twiiter, and lots more in this thread on the Home Server Show forums.
The problem was related to the built in network adapter on the microserver, whose firmware was giving the Windows updaters fits. And the only way to complete the installation was to disable the network card and replace it with an external adapter in one of the server’s two cramped expansion slots.
So, good news: there’s a fix available now, in the form of a firmware upgrade from HP.
If you have one of these servers, download the System ROMPaq Firmware Upgrade for HP ProLiant MicroServer (For USB Key-Media) and copy it to a local folder. Run the executable file SP64420.exe, plug in a blank USB key (it doesn’t have to be big), and launch the HP USB Key Setup Creation Utility. You can then boot the server from that key to flash the firmware.
I can confirm from personal experience that this works. And I should probably write up my experiences with both hardware/software combos someday..
Ed Bott (@ wordpress.com) 
I ran in to this exact problem on my N54L before there was a firmware update.
The experience and process was a royal PITA, which should never have occurred. I wasted lots of time and effort “upgrading” from WS12 Essentials to R2.
After I finally determined why the install was stalling at “Getting your devices ready 83%”, I had do the following to get my system working:
Disable the built-in Ethernet adapter via BIOS
Install WS12R2 Essentials
Attach a USB Ethernet adapter,
Figure out how to get the USB’s driver onto the N54L,
which was more difficult than you or I would imagine.
Connect to the Internet
Activate
Update
Configure, etc.
Afterwards, I bought and installed an inexpensive, dual-port, gigabit Ethernet PCIe card.
Silver Lining: If I want I can now use my box as a front-end to my domain protecting my workstations from attaching directly to the router because of the dual Ethernet ports.
Thanks for the post, even if it is too late to help me.
Good one Ed..
Ed, this isn’t directly related to the HP server but I have a question about R2 Essentials. Do you happen to use the O365 Integration Service to connect to an O365 account? Would you characterize it as ADFS “lite”?