I want to use Bootcamp to install Windows 7 on a 2011 mac mini (Windows 10 is not supported on these models). I have already created a Windows 7 image USB. I have two partitions (700GB for Mac OSX and 300 GB for Windows). Using Bootcamp when I try to install from this USB it is asking me to format the 300 GB partition in NTFS System. I have tried to use Disk Utility to format this partition in the NTFS system but I am unable to do so as this option is greyed out and not available to me. Kindly provide to me a solution to format this partition in the NTFS System without which I cannot install Windows7 on this mac mini.