LPCTSTR Dr= "H:";
      if (GetDriveType(Dr)==DRIVE_CDROM)
{
}

Value	Meaning
0	The drive type cannot be determined.
1	The root directory does not exist.
DRIVE_REMOVABLE	    The drive can be removed from the drive.
DRIVE_FIXED	                The disk cannot be removed from the drive.
DRIVE_REMOTE	    The drive is a remote (network) drive.
DRIVE_CDROM	                The drive is a CD-ROM drive.
DRIVE_RAMDISK	    The drive is a RAM disk.


GetLogicalDrives


int n;
    int nextDr=0;
    char dd[MAX_PATH];
    DWORD dr = GetLogicalDrives();

    for( int i = 0; i < 26; i++ )
	{
        n = ((dr>>i)&0x00000001);
        if( n == 1 )
        {
        dd[nextDr] =  char(65+i);
        dd[nextDr+1] = ':';
        nextDr+=2;

        }
	}
      В dd все буквы существ. дисков;