If you are going to install win 7 or Win 8 on this hard drive then "leave it blank" and just plug it in. Once done, start you installation and allow the installation to select the best partition structure for you. Now if you install Win 7 (as described above), you can expect to see a structure of two partitions. The system partition will be 100MBs and the rest will be allocated as the C drive (usually). On win 8, you will end up with two partitions as well; however, the system partition will be 350MBs and the rest (again) will be allocated to the C drive. These two scenarios are for a Legacy installation; however, the partition structure will be different if your bios supports a UEFI installation and you have that option turned on. In any case, its best to let the installation automatically set the partition structure (initially) because you can always deal with the creation of additional partitions after the install has been completed by using the disk management tools that are available in either OS.
Edited by anyrepli, 26 April 2013 - 04:18 PM.