Своим опытом делится Олег Кулабухов:

Используем ShFormatDrive:

    const SHFMT_DRV_A = 0;
const SHFMT_DRV_B = 1;

const SHFMT_ID_DEFAULT = $FFFF;

const SHFMT_OPT_QUICKFORMAT = 0;
const SHFMT_OPT_FULLFORMAT = 1;
const SHFMT_OPT_SYSONLY = 2;

const SHFMT_ERROR = -1;
const SHFMT_CANCEL = -2;
const SHFMT_NOFORMAT = -3;

function SHFormatDrive(hWnd : HWND;
Drive : Word;
fmtID : Word;
Options : Word) : Longint
stdcall; external 'Shell32.dll' name 'SHFormatDrive';

procedure TForm1.Button1Click(Sender: TObject);
var
FmtRes : longint;
begin
try

FmtRes:= ShFormatDrive(Handle,
SHFMT_DRV_A,
SHFMT_ID_DEFAULT,
SHFMT_OPT_QUICKFORMAT);
case FmtRes of
SHFMT_ERROR : ShowMessage('Error formatting the drive');
SHFMT_CANCEL :
ShowMessage('User canceled formatting the drive');
SHFMT_NOFORMAT : ShowMessage('No Format')
else
ShowMessage('Disk has been formatted');
end;
except
end
;

end;

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