How to install Windows 7 on the new 27in iMac

26 Oct 2009

Windows 7 isn't officially supported in Boot Camp just yet, but that doesn't stop it working a treat most of the time. We have it installed on one of the new MacBooks in the Labs, but the gigantic 27in iMac proved to be much more problematic (we'll have a full review of the monster in question later this week).

The problem occurs after the main Windows 7 installation has taken place. The system reboots, the Windows 7 logo circles into life and the desktop should appear - but all you get is blackness. The system is still running - press the Caps Lock key and you'll see the light ping on - but you can't see anything, indicating a problem with the iMac's ATI graphics drivers.

Fear not, though. If you've just blown £1,350 on this beautiful beast and are now scratching your head as to why you can't get it working, there is a workaround to crowbar Windows 7 onto it.

Just connect a USB keyboard and mouse, then follow these steps:

  1. Run the Boot Camp Assistant in OS X as normal and create a partition when asked, then insert your Windows 7 disc to reboot and begin the process proper.
  2. Windows 7 requires the NTFS file system, so once in the installer just select your new partition (labelled BOOTCAMP), click on Drive options (Advanced) and choose to format it. Then select the newly formatted partition and continue.
  3. Windows 7 will begin installing, and once it gets almost to the bottom of its checklist, it'll try to reboot. Now, if you leave it here, you'll get so far and see the black screen. Any further attempts to reboot will bring you to the same dead end.
  4. Instead, restart and press a key to boot from the Windows 7 disc when prompted. Rather than running the installation again, choose the little option at the bottom to Repair your computer. Decline any suggestions that pop up until you see a list of options with Command Prompt at the bottom. Choose that option.
  5. At the Command Prompt, type DEL C:\WINDOWS\SYSTEM32\DRIVERS\ATIKMDAG.SYS to delete the default ATI driver, then close the window and reboot.
  6. This time, Windows should successfully initialise a more appropriate display driver, allowing you into the desktop. From here insert your OS X disc to install the relevant hardware drivers as you normally would, then run Windows update to clear up any leftovers.

And there's a working Windows 7 installation on your new 27in iMac. Who needs official Apple support anyway?