[JRD!]

#ifdef UNICODE
  #define AW "W"
#else
  #define AW "A"
#endif

function GetDriveType(lpRootPathName: string): UINT;
  external 'GetDriveType{#AW}@kernel32.dll stdcall';

function GetMaxFreeSpaceDrive: String;
var
  i: Integer;
  sDriveRoot: string;
  iLastMax, iNewMax, iTotal: Cardinal;
begin
  iLastMax:=0;
  for i := 1 to 26 do
  begin
    sDriveRoot := Chr(i+64)+':';
    if GetDriveType(sDriveRoot) = 3 then
    begin
      GetSpaceOnDisk(sDriveRoot, True, iNewMax, iTotal);
      if iLastMax < iNewMax then
      begin
        iLastMax := iNewMax;
        Result:=sDriveRoot;
      end;
    end;
  end;
end;