D:\ -> 0x80 or -> 0x81

Edited text of question.

Alex, sounds good. That answers the first half of my question (win9x). So 222 points are yours. But how about winNT?

Thank you very much!!!   :-)

I send you programm in C in Dos(that , i hope, works in
NT , too). But i hav't NT and can't test it and rewrite
this for NT, sorry.
void cdecl main (void)
{
  struct SREGS sregs;
  union  REGS regs;
  char   DriveMapInfo[20];
  int    i;
  memset(DriveMapInfo, 0, sizeof(DriveMapInfo));
  DriveMapInfo[0] = 20;
  clrscr ();                              //clear screen
                              //clear all
  memset(&sregs , 0, sizeof(sregs));
  memset(&regs , 0, sizeof(regs));

  sregs.ds = FP_SEG(DriveMapInfo);
  regs.x.dx = FP_OFF(DriveMapInfo);
  regs.x.ax = 0x440D;                  //
  regs.x.bx = 3;                  //disk c
  regs.h.cl = 0x6F;
  regs.h.ch = 8;
  int86x(0x21, &regs, &regs, &sregs);      //read
  if ( _doserrno == 0)
    {
      char c = DriveMapInfo[3];
      char ss[3];
      i = abs(c>>4);
      ss[0] = '0' + i;
      i = c - i*16;
      ss[1] = '0' + abs(i);
      ss[2] = 0;
      printf("0x%s",ss);
      getch();
    }
}
 

It doesn't work for NT. But cause I didn't say in my original question, that I need it for both win9x and NT, I'll accept your answer... Thanx for your help!