If you machine supports UEFI, but your current install of Windows is in legacy mode (you can check by following our dualboot notes in the directions) you may not need to reinstall Windows in order to dualboot.
CREDIT WHERE IT'S DUE: Two users combined their brains to discovery this works. Read the original thread here.
talks about converting a legacy set up to UEFI. Your machine still needs to support UEFI booting for this to work, and even then there *could
* be complications so be careful trying this. However, at least 1 case confirmed this working, so we think it could help users avoid reinstalling Windows in order to dualboot.