Depending on the target version of windows, running from an SD card may be possible (see Vanderi's blog).
Backing up everything.
Using disk utility, I un-partitionned without re-installing OS-X (Select the HD, go to the 'partition' section then remove all but the boot partition and recover unused space).
Bootcamp is asking for an optical drive. I want to install windows from my SD card. This is only a warning. Ignoring it (for now).
Next it's complaining that I don't have USB drive plugged in. Confusing but, actually, bootcamp is trying to download drivers needed to run windows on my Mac.
Let's get a USB drive.
Needs to be FAT formatted.
Bootcamp tells me that it can download drivers for Windows 7. Pity, because I don't have that, which MS aren't selling anymore. No support, no problem (says Ars Technica)? Apple's compatibility chart insists that I can't.
Success story installing Win7 then upgrading.
Bootcamp is being pissy about my Windows install files sitting inside an SD card. Apple confirm it's not okay.
Maybe I can install windows 8 without Bootcamp. Software 7 blogged about it.
Windows wants NTFS but all we can make is a FAT partition, which is fine.
Back to Disk Utility let's make a FAT partition.
I now have a FAT partition, Wakugumi.
Looks like I might get a chance to install Win 8, if I hold down the option key at restart, and should expect a bumpy ride.
Nice, except it doesn't work. Proposed solution. Oh wait. Look here. And... well. After trying everything else, what worked for me was simply to make some "free space" instead of creating an actual FAT partition with Disk Utilities. Then start installing windows, and create the partition using the provided interface.
Software 7 suggests a patch to improve stability; I didn't wait to verify whether it was stable or not, I applied the patch.
Software 7 signal other issues; to mitigate this I tried running my Bootcamp drivers. The top exe refuses to run outright but I was able to run a batch of semi-randomly selected drivers, which somewhat improved the behaviour of the track-pad. Apparently it used to be possible to download the Win 8.x drivers without fuss (meaning, from Apple), no longer. Got them from a free DL site. Still waiting. Oh wait... can still download them from Apple.
- Track-pad not working. Works better now but still no 2 fingers scroll.
- Can't adjust volume and brightness. Not solved. My display is bright, and there is no sound.
Upon restarting, Windows indicates that the 'PC' needs repairing, undoes all my changes, reruns minor installation cores.
- Using BootCamp5.1.5621 as downloaded from Apple
- Installed AppleMultiTouchTrackPadInstaller64 otherwise trackpad is really sluggish. Even after installing this, you still have half of a trackpad running with no scrolling gesture, no right button. Suggestions here.
- Bypass bootcamp's compatibility check
- Run bootcamp in Windows 7 compatibility mode
- Run with enough privileges.
- Don't run via 'Setup'. Instead, run via BootCamp\Drivers\Apple\Bootcamp (depending on your package this may be called BootCamp64 or similar)
- You can disable the compatibility check by running "trouble shoot compatibility" in BootCamp context menu.
- Run the suggested command via cmd.exe.
I tried this with drivers downloaded from apple, and I tried this with the Windows 7 drivers downloaded via bootcamp. A clean re-run appeared to work fine initially. That is, until I accidentally closed the MBA's lid while installing Visual Studio. Following this, the MBA rebooted and Windows went into repair mode.