Quote Originally Posted by topgundcp View Post
I think it does matter when you install Windows using legacy MBR. If you format the drive first, Windows will not create the 350MB reserved partition and will silently install everything in C: drive. Without the reserved partition, you won't be able to use feature like bitlocker. If you leave it unallocated then Windows will create a 350MB partition. For UEFI installation, it won't matter.

Bottom line, it is best to leave it unallocated for both MBR/UEFI installation and let Windows manage it.

EDIT: BTW, Have you noticed that if you update from the previous build, Windows will create an extra 450MB Recovery partition after C: Drive ?
My two desktop PC's have legacy BIOS. The System reserved has always been added automatically for me when installing Windows 7 and 8.1. I've heard that it won't be if the drive is already partitioned when you install Windows though. If you just format but don't delete any partitions that could happen. I never manually create any partitions on a clean install. I just delete the ones Windows uses and leave my Data partition intact. YMMV I guess.

My "I don't think it matters" comment was in reference to formatting the drive, not the deleting the partitions part.