function GetCheckSum(FileName : string) : DWORD;
var
F : File of DWORD;
P : Pointer;
Fsize : DWORD;
Buffer : Array [0..500] of DWORD;
begin
FileMode := 0;
AssignFile(F,FileName);
Reset(F);
Seek(F,FileSize(F) div 2);
Fsize := FileSize(F) -1 -FilePos(F);
if Fsize > 500 then Fsize := 500;
BlockRead(F, Buffer, Fsize);
Close (F);
P := @Buffer;
asm
xor eax, eax
xor ecx, ecx
mov edi , p
@again:
add eax, [edi + 4*ecx]
inc ecx
cmp ecx, fsize
jl @again
mov @result, eax
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessage(IntToStr(GetCheckSum('c:\VasSoubor.exe')));
end;