Only tested on 13 inch-should work on the other models probably even 2012s cuz it uses quite a few bootcamp 4.0 drivers.
Not sure if anyone will ever use this but everywhere i read about this everyone just gave up and installed windows 7
Sometimes the touchpad multitouch, right clicks and tapping stop working. Right clicks can be fixed with applemou.exe. (keep reading)
Can't change brightness - I just use the intel hd control panel with different color profiles to make the screen darker
Intel HD only has 128mb ram -if anyone knows how to fix please let me know
Windows xp sp3 cd - Don't bother trying with a usb you will get nowhere. (not sure if you need ahci drivers, the cd I used already had them)
Windows 7/8 cd or usb
How to do: (I used High Sierra)
(skip this if you have win7/8 cd)First start your mac in recovery by holding command + R and go into terminal, then type "csrutil disable" then reboot normally
Then follow this guide (skip modifying bootcamp if you have win7/8 cd) but during the first reboot hold down the option key until the boot manager shows up then, put the xp cd in and boot from it, now continue the xp installation and install to the bootcamp partition.
insert an os x lion 10.7 cd or mount a lion ISO with magicdisc to install win7 32 bit drivers.
(list was made for mba 2011, so on a 2012 u might be able to use other ones on the cd (thx hackerwayne)
Since the touchpad sometimes loses the ability to right click, download this zip with the sound and wifi drivers along with a program that enables right clicking with control + click (hit command +r and type shell:startup, then put applemou.exe in the folder if you want it to start at boot
now install bootcamp with os x snow leopard cd or iso
some drivers may not installed so you can use snappy driver origin to get anything missing.