Bool DrvTypeSet(U8 drv_let,I64 type=FSt_REDSEA)
{//Very dangerous
  I64 i,j,ext_base,drv_num,offset,cur_type;
  CMasterBoot mbr;
  CBlkDev *bd;
  drv_let=Let2Let(drv_let);
  bd=Let2BlkDev(drv_let);
  drv_num=bd->first_drv_let-'A';
  switch (bd->type) {
    case BDT_ATA:
      offset=0;
      ext_base=INVALID_CLUS;
      while (TRUE) {
	ATAReadBlks(bd,&mbr,offset,1);
	j=-1;
	for (i=0;i<4;i++) {
	  cur_type=mbr.p[i].type;
	  if (cur_type) {
	    if (cur_type==5 || cur_type==15)
	      j=i;
	    else {
	      if (drv_num+'A'==drv_let) {
		switch (type) {
		  case FSt_REDSEA:
		    mbr.p[i].type=MBR_PT_REDSEA;
		    break;
		  case FSt_FAT32:
		    mbr.p[i].type=MBR_PT_FAT32a;
		    break;
		  default:
		    throw('Drv');
		}
		mbr.p[i].active=0x80;
		ATAWriteBlks(bd,&mbr,offset,1);
		return TRUE;
	      }
	      drv_num++;
	    }
	  }
	}
	if (j<0)
	  break;
	if (!mbr.p[j].offset)
	  break;
	if (ext_base==INVALID_CLUS) {
	  offset=mbr.p[j].offset;
	  ext_base=offset;
	} else
	  offset=mbr.p[j].offset+ext_base;
      }
      break;
  }
}

U0 Fmt(I64 drv_let,Bool quick=TRUE,Bool confirm=TRUE,I64 type=FSt_FAT32)
{//Format hard drive or RAM drive.
//$BK,1$Warning:$BK,0$ Destroys all prev info.
  //quick=FALSE means fill entire drive with zeros.
  //Choose $LK,"FSt_FAT32",A="MN:FSt_FAT32"$ or $LK,"FSt_REDSEA",A="MN:FSt_REDSEA"$.
  //You don't format a CD/DVD with this.
  CDrv *dv=Let2Drv(drv_let);
  Bool old_silent=IsSilent;
  if (confirm && !AreYouSure)
    return;
  if (!dv)  {
    PrintErr("Invalid Drive\n");
    return;
  }
  switch (type) {
    case FSt_FAT32:
      if (dv->bd->type==BDT_ATA) {
	Silent;
	Drv(drv_let);
	Silent(old_silent);
	FAT32Fmt(drv_let,quick);
	DskCacheInvalidate(Let2Drv(drv_let));
	Drv(drv_let);
	break;
      }
      "Using RedSea File System.\n";
    case FSt_REDSEA:
      Silent;
      Drv(drv_let);
      Silent(old_silent);
      RedSeaFmt(drv_let,quick);
      DskCacheInvalidate(Let2Drv(drv_let));
      Drv(drv_let);
      break;
    default:
      PrintErr("File System Not Supported\n");
  }
}