Get the CDROM drive letter

[Function declarations]
FUNCTION ulong GetLogicalDrives() LIBRARY "Kernel32.dll"
FUNCTION uint GetDriveType( Ref String as_root_path ) LIBRARY "kernel32.dll" ALIAS FOR "GetDriveTypeA"
[PB function String of_GetCDRootPath()]
integer li_ctr
string ls_root
ulong lul_drives, lul_rem
lul_drives = GetLogicalDrives()
DO
lul_rem = MOD(lul_drives, 2)
IF lul_rem = 1 THEN
ls_root = Char(li_ctr + 64) + ":\"
IF GetDriveType(ls_root_path) = 5 THEN
Return ls_root_path
END IF
li_ctr ++
END IF
lul_drives /= 2
LOOP UNTIL lul_drives = 0
RETURN ""