Em particular:
8.On the Where do you want to install Windows? page, do one of the following:
•In Windows 8.1, tap or click the partition that you want, tap or click the formatting option you want to perform if needed, then follow the instructions.
•In Windows 8, tap or click Drive options (advanced), tap or click the partition that you want to change, tap or click the formatting option you want to perform if needed, then follow the instructions.
Isso permitirá que você remova quaisquer partições existentes, crie novas, formate-as e instale 8.1 onde desejar.