Originally Posted by biren
No, you don't have to reinstall Windows, however, it is far easier to reinstall, as not reinstalling will require a Linux live CD, a Windows install CD, command lines in Linux, command lines in Windows, and an acute understanding of the Windows boot loader/BCD.
You actually don't need secure boot. It does provide a tiny amount of security, but it is security mostly against targetted attacks.
You do however want to UEFI boot. It is incredibly faster than legacy.
Legacy requires an MBR-style disk, UEFI requires a GPT style disk. You can easily convert the disk at install time, but you will need to format the whole thing.
You must disable legacy mode, boot the install cd in UEFI mode (from the BIOS/UEFI boot menu), and procede to install after a disk format.
Press Shift + F10 ojce you UEFI boot the installation CD.
Enter the following, substitute '0' for the disk number of the target disk you want to install to. It will displayed after 'lis dis'.
DiskPart> lis dis
DiskPart> sel dis 0
DiskPart> conv dis