Then use System Information to see what your Mac currently has.When you buy Windows, it comes as a disk image file (ISO) that you download, or as an installation disc or USB flash drive.If you're installing Windows for the first time, make sure the Windows installer you're using is for a full installation (not an upgrade installer).You can upgrade existing 64-bit installations of Windows 7, or 8.1 to Windows 10.Some very interesting changes in how Windows is installed in Boot Camp on OS X 10.11 “El Capitan”.
The Boot Camp Assistant will download Windows support software, partition the disk, and copy the necessary Windows files to get started.After Boot Camp Assistantd completes, OS X restarts to the Windows installer, and you follow the normal Windows installation. Where is the Windows installer if there is no installation media?Boot Camp Assistant doesn’t just create a Boot Camp partition, but also creates an additional partition called “OSXRESERVED” that is FAT32 formatted.Some versions of Windows require a certain processor and more hard drive space and memory (RAM) than others.Check the documentation that came with your copy of Windows to find out what you need.It places this partition right after the recovery partition, and before the Boot Camp partition, as shown below. Partition 1 is the standard EFI partition, partition 2 is the Mac partition, partition 3 is the Recovery partition. Partition 4 is now the OSXRESERVED partition, and partition 5 is the BOOTCAMP partition.