If it's one HDD, it's a bad idea to have multiple partitions since it tends to laden the HDD with more tasks than it can handle. If it's one SSD, you can't partition it(as it'll just kill it) and you don't have any storage space for your critical data. I'd advise on having an SSD as the primary(boot/game) drive and have a mechanical drive to cater to storage needs with 2 partitions on it.