For drawing maps I use a G.I.S. program, and in the setup of the program you have to specify drive letters and paths for the maps to store and the backup files to be placed.
The program has one advantage: it is not necessary to install the program, you can copy it from one computer to an other, or onto an USB drive and run it from there, on any computer.
That last is the problem, the drive letter assignment is stored in Windows, not on the USB device.
On my two computers at home it runs under X:, but as soon I place it in an other computer it gets the first free letter, and the program will not work because it can not find the X: drive.
I have tried USBDLM but I cannot get it to work, is there an other way to solve my problem?