procedure WipeFile(FileName: string);
var
buffer: array [0..4095] of Byte;
max, n: LongInt;
i: Integer;
fs: TFileStream;

procedure RandomizeBuffer;
var
i: Integer;
begin
for i := Low(buffer) to High(buffer) do
buffer[i] := Random(256);
end;
begin
fs := TFilestream.Create(FileName, fmOpenReadWrite or fmShareExclusive);
try
for i := 1 to 3 do
begin
RandomizeBuffer;
max := fs.Size;
fs.Position := 0;
while max > 0 do
begin
if max > SizeOf(buffer) then
n := SizeOf(buffer)
else
n := max;
fs.Write(Buffer, n);
max := max - n;
end;
FlushFileBuffers(fs.Handle);
end;
finally
fs.Free;
end;
Deletefile(FileName);
end;