According to the link below, I should be able to install and run the full version of Windows 8.1 Pro (64-bits) on a mid 2010 iMac 27 using Boot Camp Support Software 5.1.5640. http://support.apple.com/kb/DL1721 When I do this on a fully up to date Mavericks install, getting the Boot Camp Assistant to partition the SSD I use as my main drive and allowing it to select and download the support software, everything goes swimmingly until I reboot after installing the Support Software. I've tried various things including: 1) Updating the Windows install prior to installing the Support Software. 2) Installing previous versions of the Support Software (5.0.5033 and 4.0.4033) I've flattened the partition after each attempt and allowed the Boot Camp Assistant software to create a single OS X partition before each new attempt. The problem I see is a blue screen on reboot with the message KERNEL_SECURITY_CHECK_FAILURE. What I wanted to check is if anyone has a working install of Windows 8.1 Pro (64-bit) on a mid 2010 imac 27 model and if they had to do anything special in the process? Additional information. The iMac has 16GB of memory and the SSD is 250GB with 150 GB free space prior to creating the Windows partition to which I'm assigning 80GB. I'm using a full length Apple standard wired keyboard. I've disconnected everything from the iMac apart from the keyboard and mouse during the installation and am trying to make everything as standard as possible.