So I just spent the past 5 hours trying to install Windows 7 via BootCamp on my new 27" iMac. It would get past the initial installation and then after the final reboot just before it runs off the hard drive and asks you for a serial number, the screen would go black and I couldn't do anything. So I found this solution here: http://geekswithblogs.net/ajames/ar...an-imac-and-windows-7-rtm-ndash-and-have.aspx Except the instructions on that site are for an iMac with an NVIDIA Graphics Card. The 27" iMac has an ATI card. So at step 6 I deleted the file named: ATIKMDAG.SYS from the same directory. Then clicked restart and was able to finish through the install process. Summary: (from a response below) The way the iMac 27" DisplayPort works in the system, when installing windows it will output to BOTH the iMac screen and DisplayPort. When Windows 7 install is reaching a certain point it is making a choice as to which display it believes it the primary display. If you have a display plugged into your iMac's display port or have that ability you will see your install is working just fine, the problem is just that windows believes the active displayport on the back of the iMac is the primary display and moves all video to the port.. that is why you see a black screen. Rebooting and doing the driver deletion steps does work as it will allow windows to run on a generic driver unable to make that choice. Note: you will need an additional monitor and a Mini-Display Port adapter to plug the monitor into the iMac to use the above method. The BootCamp driver that loads only give a max resolution of 1980 X 1440 so everything looks stretched. Installing the ATI drivers from ATI did no good. (See the update below to fix this) Also be aware that only the keyboard will be active during the install so you will need a usb mouse unless your really good at navigating Windows with only a keyboard. UPDATE: After installing Windows 7 if you run windows update there is an update available for the ATI card. Once installed and restarted the resolution is now fixed. When you go into the resolution settings in Windows 7 the display now shows up as a color LCD and the max available resolution is 2560 x 1440.