procedure TForm1.Button1Click(Sender: TObject);
var
Size: Cardinal;
hKey: Windows.HKEY;
Buffer: ShortString;
Str: string;
begin
RegOpenKey(HKEY_LOCAL_MACHINE, 'software\microsoft\windows nt\currentversion', hKey);
Size := SizeOf(Buffer);
RegQueryValueEx(hKey, 'productname', nil, nil, @Buffer, @Size);
Str := string(PChar(@Buffer)) + ' (Build '; Size := SizeOf(Buffer);
RegQueryValueEx(hKey, 'currentbuildnumber', nil, nil, @Buffer, @Size);
Str := Str + string(PChar(@Buffer)) + ') ';
RegQueryValueEx(hKey, 'csdversion', nil, nil, @Buffer, @Size);
Str := Str + string(PChar(@Buffer));
RegCloseKey(hKey);
Caption := Str;
end;