you need an ISP cable. Usually you can make such a cable connected to the parallel port of your PC, but you will soon after be posting asking why it doesn't work. No offense, this setup is not really reliable since all parallel ports are different. You would be better off building or buying a usbasp programmer which is very reliable. Search this forum for 89S51 ISP programming. You will find some links with source code and schematic diagrams.
If you are dead set on building a parallel port cable, search Google for Adam Dybkowski, ISP programmer. Use this software with the cable.