Didn't know you could fry the PS/2 port by hotplugging it. I discovered by accident that a PC will hang if you pull out a PS/2 cable while it's running - or at least this was the case way way back when, not sure if winXP was even released at the time so it may not be true anymore.
Frying happens with the really old keyboards which draw like 10x the current of the more modern ones. If it doesn't have Windows keys, is so heavy it can be used as a lethal weapon, and the date written on the back is from when the USSR still was around, beware.
most people building the PC for the first time are not going to need to play with the "UEFI" settings much or at all, current motherboards will work perfectly with default settings basically, specially if you only have more than one or two HD, maybe an optical drive or usb drive for installing windows 7/8, or if steam OS is developed to a point it offers the same kind of experience,
But it gets hairy with dual boot. "It works when I do nothing with it" is often true of desktop linux as well, your firefox vlc and stereo sound will work but when you want to share a folder, have 5.1 or play games you might have to fight a battle with lots of stuff and learn too many things.. The linux situation has greatly improved though so with a modern one and mainstream enough desktop you can e.g. share a folder by right-clicking it.
I really have a non-technical friend who wants to dual boot, he was used to Ubuntu (gnome 2) for daily use, now that will be Mint with Mate (gnome 2 still lives on) and he simply wants Windows for occasional gaming and especially LAN gaming.
The bad UEFI behaviour was Windows 7's fault actually. I just ran the installer, it refused to install and after that the boot entry called "linuxmint" was corrupt and is unfixable till I learn to fix it. I lost a lot of my time.
The motherboard was very recent btw (micro ATX FM2+, 2014), is made by Asrock which I trust for BIOS features and support.
I can see that kind of stuff be a problem for Valve's Steam OS, customers might want to dual boot it with Windows and bork things.