Our research shows that, overall, approximately 3.1% of PCs that have one physical hard drive also have an unutilized partition with drive letter D:. Our research indicates that 4.8% of portables and 2.4% of desktops have a D: drive partition that has 99% or more free space. It appears that it is common for some vendors to split the primary hard drive into two partitions. Often a drive is split into two equal partitions. If you think your hard drive capacity isn’t what you paid for, you might want to check to see if you have an unutilized drive partition.