I was thinking about this the other day in the lab. I was thinking many people know about floppy drives and the a:\ drive being the default, but the b:\ drive? That is a different story. In the old days the OS would boot from the floppy and it was considered the a:\ drive. I assume that some low level boot code was hard coded to path a:\ and that’s why the a:\ was reserved (I assume this is still the case to some extent), but the b:\ drive became the removable drive because people with 2 drives could not only copy data between drives, but they had the luxury of just leaving the boot floppy in drive a:\ if they wanted. Hard drives came along later and became the c:\ drive. This is interesting that even in the modern world of Windows 10 that the boot drive defaults to c:\. How legacy.