A recent acquisition the new 27" iMac presented me with a brief challenge when I went to install Windows 7 with Bootcamp; after the first stage of the install the screen remains blank.
A quick search on the internet presented a very concise solution on the UK PCPro site, thanks guys.
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.