You have a partition no matter what. It is just the entire disk is a single partition. A partition is a necessary ingredient in organization of the disk. Now, if your question is do you need MORE THAN ONE partition, that is a slightly different question. IF you have only a single disk, then splitting it to say 200GB for a C: drive and the rest for a D: drive makes it easy to clone the C: drive to an SSD when you have the $$$$.