It has come to light, that a UEFI installed system, will fail to boot if a secondary drive is attached which contains logical partitions. This would have to be an MBR configured drive, of course, but if it has at least one primary and one extended partition, it will stop Windows 7 and Windows 8 from booting. This can be a significant problem for several reasons. First, most folks that have UEFI installs do not even know. Secondly, information about extended or logical partitions on a secondary drive will not normally be given by a poster. I can see this occurring in situations where someone gets a new system and attaches their old drive to recover data... And I should add, if the drive is connected during a Windows 7 install, the install will fail during the first reboot.