PS4 format erases all partitions and uses the entire drive for game storage, unreadable on PC (unless you repartition/format it to Windows Format … which will wipe your games)
Extended game storage can only be used on PS4 for extra game storage, nothing else.
Oh, I see.Your solution is also another problem that i’ve been looking for to solve. What is the easiest way to reformat this HDD to use it on Windows again?
go into Windows Disk Management and you’ll see an “Unknown Disk” (in my case my PS4 Extended Storage HDD is Disk 2) and you’ll be prompted to Initialize Disk (Partition) it … then after partitioning it, format it however you want eg. NTFS, exFAT etc