Good question. In what context? I ASSumed that "VB" implied Windows, but using dx rather than edx looks like 16-bit code. Is VB6 16-bit? (told ya I didn't know VB!) In any case, my recollection is that dos assigns drive letters based on... "drive C:" is whatever it boots from, then "drive D:" etc. are assigned... primary partitions first, then "extended" partitions (if any). I might remember that wrong. BIOS calls whatever it boots from "80h" (assuming it's a hard drive, not a floppy). Changing the "boot drive" in BIOS setup, and/or adding/subtracting partitions with fdisk, will change these assignments. I've been known to format the wrong drive!
I would think (guessing!) that to "clone" a drive, you'd be interested in physical drives, not partitions. I would think that BIOS interrupts would be much more useful than dos interrupts (pretty useless, I would expect!). As I recall, Windows has APIs for "raw disk" access, which is what you'd want, I think. "Fake dos" probably won't work (guessing!).
Where the heck are we?
Best,
Frank
