INT 2F - CD-ROM v2.00+ - GET CD-ROM DRIVE LETTERS
AX = 150Dh
ES:BX -> buffer for drive letter list (1 byte per drive)
Return: buffer filled with drive numbers (0=A:).  Each byte corresponds
to the drive in the same position for function 1501h

See also: 2F150B

2F150D - CD-ROM v2.00+ - GET CD-ROM DRIVE LETTERS