XP Home Edition SP2. Disk Director Suite version 10 build 2,117. I need to allocate a drive letter to a partition on one of my two external hard drives but none are available in Change Letter. The last one I used was Z:. Drive letters K: to N: are not used but are inaccessible. Is there any way to make these available so that Windows Explorer can recognise the partition? Any advice would be much appreciated. hac32.