In theory, it's fine. The SUBST command disappear next boot. however, it wont work for you, as you will need to do something similar to: D = G E = I F = D and you have a connflict. Windows defines those letters in a fixed, standard manner. I play with partition placement, and hiding until setup is completed. I do rename the CDs, and use the SUBST commnd to hold over till the reboot, but the letters I use are always available in my boxes (K, L, ... )