Prologue: Apple et al recommend you “install new OS’s from USB, not DVD – USB is faster”, but I’ve never bothered before. However, there appears to be a major defect in most Apple iMacs, where the DVD drives fail after only a dozen or so uses (google it and there’s depressingly-long forum threads of people reporting the same problem). When this hit my iMac, I was forced to explore the USB alternatives…
Windows 8 boots the same way Macs do
With the arrival of Windows 8, much of what we see on the web about “installing windows” or “booting windows” is wrong — including Apple’s own Bootcamp (currently: almost a year out of date, badly broken, and Apple hasn’t announced a fix. Sigh).
Allegedly (confirmed by direct experience, but I’m no expert on this) – Windows 7 (and previous versions) used “MBR” booting. Intel Macs use the more modern “GPT” booting – and Windows 8 has finally dropped backwards compatibility, and uses GPT too.
So, as of 2013: there is nothing “special” needed to make a Mac boot in Windows 8
In fact, if you try to, Windows 8 install WILL FAIL because it doesn’t support the old MBR booting any more (it even produces a clear, helpful error message explaining why)…
If something ruins your booting, fix from command line
For power-users who know what they’re doing, this stack-exchange answer gives good step-by-step instructions (with explanations!) on how to “un-break” a broken boot setup on Mac. Worth bookmarking (I used it to fix one of my machines).
NB: all the tools they use in that answer are pre-installed with the Mac and have “man” docs – type “man (command name)” in Terminal to read them.
NB: you can run these tools straight away, but they will probably refuse to “save changes” because you’re using the disk they’re trying to change (mentioned in the link above). You’ll need to boot into a special “repair mode” – see below:
NB: if you mis-type the instructions on that page, you probably will wipe your hard disk. Don’t try this while tired/drunk/etc – or at least take a full backup of your computer first!
An OS X “emergency boot USB drive” is only 1GB
The web is plagued with technically unskilled “journalists” who write articles about “make a USB boot disk for OS X”, and all they do is copy/paste Apple’s own instructions on how to INSTALL OS X (and then they claim credit for it).
The OS X installer requires a 4GB – or, if you’re unlucky, an 8GB – USB key. That’s 8x what you actually need.
It is faster, easier, and safer to use Apple’s own “Make an OS X Bootable USB key” app, which works on any USB drive that’s 1 GB or larger.
You can even create the USB key without downloading the special app – although it requires more fiddling (I recommend: download the app. It’s small and trivial to use).
NB: if you own a mac, make one of these now. Do something useful with those crappy 1GB USB keys you have gathering dust on the shelf!
OS X has an Emergency Partition by default – but you can’t use it
Because those USB boot disks are so massively valuable, Apple now includes a hidden one on your hard disk too, so that you can boot into that and “fix” your main OS X even if you don’t have a USB drive.
Here’s more info on the “Recovery Partition” as its called.
HOWEVER: since that’s installed on the same disk you’re partitioning, … most / all of the disk-repair / disk-alteration utilities are still disabled. That’s why you want/need a USB emergency disk!
Apple’s emergency boot disk doesn’t support all USB devices (e.g. some mice)
Even devices that work during the Apple boot-menu are DISABLED BY APPLE in their “emergency repair / boot” setup.
But without a mouse, you cannot get to the OS X menubar.
And Apple designed their “emergency” system so that most of the features can ONLY be reached viw the menubar (hmm. They really didn’t think that one through…)
So, memorize this keyboard shortcut: ctrl-f2 (or, on a wireless keyboard or laptop: fn-ctrl-f2).
That hilights the “apple symbol” menu, and you can then use cursor keys to reach the other menus.
Apple won’t let you create a USB Windows installer unless you have a MacBook Air
Someone at Apple went out of their way to make life miserable for Apple customers. If you own (or can borrow) a MacBook Air, Apple’s Bootcamp enables an extra “magic feature”: it will create the Windows 8 install USB key for you. (NB: requires a 4GB or greater USB key).
…but if you try this on any other physical Mac, Apple blocks that feature. The key you create will work on EVERY Mac – there’s nothing magical about it.
NB: if you have a Windows 8 DVD but don’t own an Air, and you know someone who does, it’s probably worth borrowing theirs now, to make one of those keys, in case you need it later!
NB: alternatively, if you have access to a machine that already has Windows installed, you can use Microsoft’s “create a Windows8 boot disk / installer” app (says win7, but works for win8 too). Unless you have a recent version of Windows, though, you’ll need to download hundreds of megabytes of .NET updates before this will run – which makes this a slow and irritating option.