how do drive letters get assigned?
, letters on non-LVM systems are assigned anew on every boot in a fixed order. Letters are said to shift when a partition is hidden or removed which previously had a lower letter assignment than the partitions remaining, which causes those remaining partitions each to take a lower letter than previously; or, a partition is unhidden or added, which due to its location other than last, takes a letter that had previously been used by a partition which remains, consequently taking a higher letter. Problems from letter shift arise on multiboot systems because of installing an operating system or systems on either logical partitions or second disks. OS boot installations depend for every boot on retaining the same letter as assigned during install. Their configuration and ini files have the boot drive letter incorporated and will not permit successful startup when the expected drive letter is not the actually assigned drive letter.
